Tire

Abstract

To provide a tire that can suppress separation with a belt end as a starting point.SOLUTION: The tire comprises sipes formed on a tread face, dimples having portions communicated with the sipes in a grounding end area, and belts laminated on outside in a tire radial direction of a carcass. The belt includes a first belt ply whose width in a tire axial direction is widest of a plurality of belt plies constituting the belt and a second belt ply laminated on outside in the tire radial direction of the first belt ply, in which the other member is not intervened between a tread rubber and the ply. A first rubber layer which is lower in complex elastic modulus than the tread rubber is formed on at least an outer peripheral surface of the first belt ply. The portions communicated the sipes are arranged at a position overlapping with the first rubber layer, in a planar view of a tread.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to tires. [Background technology]

[0002] Patent Document 1 discloses a tire in which a sipe-dimple connection is provided in the tread edge region. The tread edge region is prone to relatively large vibrations during running, and vibrations are particularly likely to be large at the connection portions provided in the tread edge region. If the vibrations are transmitted to the belt, there is a risk of the belt becoming distorted.

[0003] By laminating the belt cover disclosed in Patent Document 1 on the outer side of the belt in the tire radial direction, such belt distortion can be suppressed. However, some tires do not have a belt cover depending on the speed symbol. In such tires, vibrations during driving are directly transmitted to the belt, so the belt distortion is likely to become large, and there is a risk of separation starting from the belt end. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2015 / 166802 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present disclosure is to provide a tire capable of suppressing separation originating from a belt end. [Means for solving the problem]

[0006] The tire disclosed herein includes sipes provided on a tread surface, dimples having connecting portions with the sipes in a ground contact edge region, and a belt laminated on the tire radial outside of a carcass, the belt including a first belt ply having the widest width in the tire axial direction among a plurality of belt plies constituting the belt, and a second belt ply laminated on the tire radial outside of the first belt ply and having no other member interposed between it and tread rubber, a first rubber layer having a complex elastic modulus lower than that of the tread rubber is provided on at least an outer peripheral surface of the first belt ply, and the connecting portions are provided at a position overlapping with the first rubber layer in a plan view of the tread. [Brief description of the drawings]

[0007] [Figure 1] FIG. 2 is a tire meridian cross-sectional view showing a tire according to the present embodiment. [Diagram 2] Development diagram showing the tread pattern [Diagram 3] A tire meridian cross section showing the main parts of the tire [Figure 4] FIG. 2 is an enlarged view showing an axially outer end of a first belt ply of a tire; [Diagram 5] Enlarged view of the main part of the tread surface [Figure 6] FIG. 1 is a perspective view showing a main part of a tread surface. [Figure 7] Cross-section along the center line of the sipe [Figure 8] Cross-sectional view of Figure 5 taken along the arrow XX [Figure 9] Enlarged view of the main part of the tread surface [Figure 10] A development view showing a modified tread pattern DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] An embodiment of the present disclosure will be described with reference to the drawings.

[0009] [tire] The tire T of this embodiment shown in FIG. 1 is a pneumatic radial tire for automobiles having a pair of beads 1, sidewalls 2 extending from each of the beads 1 in the tire radial direction outward, and a tread 3 continuing to the tire radial direction outer ends of each of the sidewalls 2. An annular bead core 1a is embedded in the bead 1. The bead core 1a is formed by covering a bundle such as a steel wire with rubber. A bead filler 1b is disposed on the tire radial direction outer side of the bead core 1a. The bead filler 1b is formed of rubber with a triangular cross section extending from the bead core 1a in the tire radial direction outward. A tread surface 3f of the tread 3 is formed of a tread rubber 3a. The tread rubber 3a may include a cap rubber having the tread surface 3f and a base rubber provided on the tire radial direction inner side of the cap rubber.

[0010] Here, the tire radial direction is the direction along the diameter of the tire T, and corresponds to the up-down direction in FIG. 1. In FIG. 1, the upper side is the outer side in the tire radial direction, and the lower side is the inner side in the tire radial direction. The tire axial direction is a direction parallel to the rotation axis of the tire T, and corresponds to the left-right 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 located at the center of the tire T in the axial direction, and is a virtual line perpendicular to the tire rotation axis in a plan view of the tread. The tire circumferential direction is the direction around the rotation axis of the tire T.

[0011] The tire T includes a carcass 4 extending in a toroidal shape across a pair of beads 1. The carcass 4 is wound up from the inside to the outside in the tire axial direction so as to sandwich the bead cores 1a and the bead fillers 1b. The carcass 4 is formed of a carcass ply formed by rubber-coating carcass cords. The carcass cords are aligned in a direction intersecting the tire circumferential direction (for example, in a direction at an angle of 75 to 90 degrees with respect to the tire circumferential direction). Metals such as steel, and organic fibers such as polyester, rayon, nylon, and aramid are preferably used as materials for the carcass cords.

[0012] The tire T includes a belt 5 laminated on the outer side of the carcass 4 in the tire radial direction. The belt 5 is formed of a plurality of (two in this embodiment) belt plies 5a, 5b laminated on each other. The belt plies 5a, 5b are each formed by rubber-coating belt cords. The belt cords are aligned in a direction inclined with respect to the tire circumferential direction (for example, in a direction at an angle of 20 to 30 degrees with respect to the tire circumferential direction). Metal such as steel is preferably used as the material for the belt cords. The belt plies 5a, 5b are laminated such that the belt cords cross each other in opposite directions between them.

[0013] There is no other member between the belt 5 and the tread rubber 3a (base rubber). That is, the tire T does not include a belt reinforcing material covering the outer side of the belt 5 in the tire radial direction. Only the tread rubber 3a is provided on the outer side of the second belt ply 5b in the tire radial direction. The belt reinforcing material is formed by a belt reinforcing ply formed by rubber-coating belt reinforcing cords. The belt reinforcing cords are aligned substantially parallel to the tire circumferential direction. The belt reinforcing ply is formed, for example, by winding one or more rubber-coated belt reinforcing cords in a spiral shape along the tire circumferential direction. As the belt reinforcing material, a cap ply that covers the entire axial direction of the belt 5 or an edge ply that covers the end of the belt 5 is known, but the tire T does not include either a cap ply or an edge ply. The belt reinforcing material is provided, for example, in tires with a speed symbol of H or higher, and is not provided in tires with a speed symbol of S or lower.

[0014] The tire T includes an inner liner 7 provided on the inner surface of the tire T. The inner liner 7 is formed of rubber having excellent air blocking properties, such as butyl rubber. The inner liner 7 has a function of maintaining the internal pressure of the tire T.

[0015] [Tread pattern overview] A tread pattern shown in FIG. 2 is formed on a tread surface 3f, which is the outer peripheral surface of the tread 3. As shown in FIG. 2, the tire T has a plurality of main grooves 10 extending in the tire circumferential direction (corresponding to the vertical direction in FIG. 2) on the tread surface 3f, and a plurality of lands 20 partitioned by the main grooves 10. The main grooves 10 are provided with a wear indicator (not shown). The main grooves 10 have a maximum groove width of 4 mm or more and a maximum groove depth of 5 mm or more. The groove width is measured as the distance between the intersection points of the surface of the land 20 and the groove wall in a direction perpendicular to the extension direction (length direction). The same applies to the groove width of the lug grooves 30 and the width of the sipes 40 described later. The main grooves 10 are straight grooves, but are not limited thereto and may be zigzag grooves.

[0016] The dimensions of the main groove 10, the lug groove 30, the sipes 40, the dimples 70, the ground contact width GW, and the like described above are measured in a no-load state with the tire T mounted on a regular rim and inflated to a regular internal pressure. 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 internal pressure is an air pressure that is determined for each tire by each standard in the standard system including the standard on which the tire is based, and in the case of truck and bus tires and light truck tires, it is the maximum air pressure for JATMA, the maximum value 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 180 kPa, but for tires listed as Extra Load or Reinforced, it is 220 kPa.

[0017] In this embodiment, three main grooves 10 are provided on the tread surface 3f, and four lands 20 are defined by the three main grooves 10. The three main grooves 10 include a pair of shoulder main grooves 11, 13 located axially outermost among them, and a center main groove 12 located between the pair of shoulder main grooves 11, 13. The center main groove 12 is provided on the tire equator TC. The four lands 20 include a pair of shoulder lands 21, 24 formed adjacent to the axially outer side of the shoulder main grooves 11, 13, and a pair of quarter lands 22, 23 formed adjacent to the axially inner side of the shoulder main grooves 11, 13.

[0018] The shoulder lands 21, 24 each include a ground contact end TE. The ground contact end TE is the outermost position in the tire axial direction of the ground contact surface when the tire T mounted on a standard rim is inflated to the standard internal pressure, placed vertically on a flat road surface, and a standard load is applied. The standard load is a load determined for each tire by each standard in a standard system including the standard on which the tire is based, and is the "maximum load capacity" for JATMA, the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and "LOAD CAPACITY" for ETRTO. If the tire is for passenger cars, the load is equivalent to 88% of the above load. If the tire is for racing karts, the standard load is 392N.

[0019] Each of the multiple lands 20 has a lug groove 30 (lug grooves 31 to 33) and a cut-shaped sipe 40 (sipes 41 to 45) formed therein, which extend in a direction intersecting with the tire circumferential direction. The lug groove 30 has a groove width exceeding 1.5 mm, and preferably has a maximum groove width of 1.8 mm or more. The lug groove 30 has a maximum groove depth of preferably 3.0 mm or more, more preferably 4.4 mm or more. The maximum groove depth of the lug groove 30 is equal to or less than the maximum groove depth of the main groove 10. The sipe 40 has a maximum width of 1.5 mm or less. The sipe 40 has a maximum depth of preferably 2.0 mm or more, more preferably 3.0 mm or more. The maximum depth of the sipe 40 is equal to or less than the maximum depth of the lug groove 30.

[0020] In this embodiment, a tread pattern is formed that is asymmetric with respect to the tire equator TC. The tire T is a mounting direction specified tire in which the mounting direction relative to the vehicle is specified. The inner region IN is a region that is on the inner side of the vehicle (inside side) when mounted on the vehicle with reference to the tire equator TC, and the outer region OUT is a region that is on the outer side of the vehicle (outside side) when mounted on the vehicle with reference to the tire equator TC. The shoulder land 21, the shoulder main groove 11, and the quarter land 22 are each provided in the inner region IN. The quarter land 23, the shoulder main groove 13, and the shoulder land 24 are each provided in the outer region OUT.

[0021] An indication for designating the mounting direction relative to the vehicle is provided on the outer surface of the tire T. The mounting direction is designated, for example, by providing an indication indicating the vehicle inner side (e.g., "INSIDE") on the outer surface of the sidewall 2 that is disposed on the vehicle inner side when mounted on the vehicle, and / or by providing an indication indicating the vehicle outer side (e.g., "OUTSIDE") on the outer surface of the sidewall 2 that is disposed on the vehicle outer side when mounted on the vehicle. Note that the tire T is not limited to a mounting direction designated tire, and therefore may have a tread pattern that is symmetrical with respect to the tire equator TC.

[0022] [Belt end peripheral structure] The tire T has sipes 45 provided on the tread surface 3f, and dimples 70 having communicating portions CP1 with the sipes 45 in the ground contact edge region EA. In a plan view of the tread, the ground contact edge region EA is a band-shaped region centered on the ground contact edge TE. The axial width DW of the ground contact edge region EA is 20% of the ground contact width GW. In other words, the axial distance from the ground contact edge TE to the axial end of the ground contact edge region EA is 10% of the ground contact width GW. The ground contact width GW is the dimension in the axial direction of the tire between the ground contact edges TE, TE.

[0023] The sipes 45 have a constant width and extend in the tire axial direction across the ground contact edge TE. The sipes 45 are curved to be convex in the tire circumferential direction. The sipes 45 and the dimples 70 are provided on the shoulder land 24 including the ground contact edge TE among the multiple lands 20.

[0024] An axially inner end (one end) of the dimple 70 communicates with the sipe 45. This increases flexibility of the area between adjacent lug grooves 33 (described later) and improves ground contact at the shoulder land 24. An axially outer end (the other end) of the dimple 70 terminates within the buttress 9. The buttress 9 is the radially outer area of ​​the sidewall 2 (see FIG. 1).

[0025] At least a portion of the dimple 70 is provided at a position overlapping with the ground contact edge region EA. This allows the dimple 70 to deform during cornering, dispersing (uniformizing) the ground contact pressure and suppressing uneven wear in the shoulder land 24 (greater wear on the axially outer side of the shoulder land 24 than on the axially inner side of the tire). In this embodiment, the communication portion CP1 (dimple 70) is provided axially outward of the ground contact edge TE, but is not limited to this. The communication portion CP1 (dimple 70) may be provided axially inward of the ground contact edge TE or so as to cross the ground contact edge TE.

[0026] In one example, the width of the dimple 70 is substantially the same as the width of the sipe 45 at the communication portion CP1. The width of the dimple 70 increases from the communication portion CP1 toward the outside in the tire axial direction. The maximum width of the dimple 70 is at least twice the width of the sipe 45. Note that the width of the dimple 70 may be larger than the width of the sipe 45 at the communication portion CP1, or the dimple 70 may have a constant width.

[0027] In one example, the dimple 70 is formed in a crescent shape that is relatively narrow at both ends in the tire axial direction and relatively wide at the center. The dimple 70 is curved so as to be convex in the same direction as the sipes 45 in the tire circumferential direction.

[0028] The dimple 70 has a maximum depth of, for example, 1.0 mm or less. In one example, the depth of the dimple 70 is 0.5 mm at the axially outer end of the tire, gradually increases from there toward the ground contact end TE, and is 0.8 mm at the communication portion CP1. In one example, the depth of the dimple 70 at the communication portion CP1 is smaller than the depth of the sipe 45 at the communication portion CP1.

[0029] As shown in Fig. 3, the belt 5 includes a first belt ply 5a and a second belt ply 5b laminated on the tire radial direction outer side of the first belt ply 5a. The first belt ply 5a is formed to be wider than the second belt ply 5b. That is, the first belt ply 5a is the belt ply that is widest in the tire axial direction among the multiple belt plies that constitute the belt 5.

[0030] The axial distance SD between the axially outer end 5aE of the first belt ply 5a (hereinafter simply referred to as the "outer end 5aE") and the axially outer end 5bE of the second belt ply 5b (hereinafter simply referred to as the "outer end 5bE") is preferably 4 mm or more. This makes it possible to suppress an increase in vibration of the end of the belt 5 due to an increase in the weight of the end of the belt 5, and to suppress separation starting from the end of the belt 5. In addition, it is possible to suppress an increase in the thickness of the end of the belt 5, and to suppress air pockets at the end of the belt 5 during tire manufacturing. The distance SD is preferably 8 mm or less. This makes it possible to ensure the effect of improving tread rigidity by providing the belt 5. In one example, the distance SD is 6 mm.

[0031] An outer end 5aE of the first belt ply 5a is provided axially outboard of the ground contact edge TE in the ground contact edge region EA in a plan view of the tread. The same is true for an outer end 5bE of the second belt ply 5b.

[0032] At least the outer peripheral surface of the first belt ply 5a is provided with a first rubber layer 8a having a lower complex elastic modulus than the tread rubber 3a (cap rubber) forming the tread 3. That is, the first rubber layer 8a is formed of a rubber having a higher cushioning property than the tread rubber 3a (cap rubber). This allows the first rubber layer 8a to absorb vibrations transmitted to the belt 5, suppressing distortion of the belt 5 due to vibrations and suppressing separation starting from the end of the belt 5. The first rubber layer 8a is preferably formed of a low heat generation rubber. This suppresses heat generation in the first belt ply 5a and prevents damage to the belt 5.

[0033] The complex modulus of the first rubber layer 8a is preferably 20 MPa or less. The complex modulus is a value measured using a viscoelasticity spectrometer manufactured by UBM under the conditions of a temperature of 23°C, an initial strain of 10%, a dynamic strain of ±3%, and a frequency of 10 Hz. As described above, the complex modulus of the first rubber layer 8a is smaller than that of the tread rubber 3a. The complex modulus of the first rubber layer 8a is preferably smaller than that of the topping rubber of the first belt ply 5a. In order to suppress heat generation at the belt end, the complex modulus of the first rubber layer 8a is preferably 13 MPa or more. The complex modulus of the first rubber layer 8a is not limited to the above, and may be 10 MPa or more.

[0034] The loss tangent tanδ of the first rubber layer 8a is preferably 0.17 or more. The loss tangent tanδ is a value measured in accordance with JIS K6394:2007 under the conditions of a temperature of 23°C, a frequency of 20Hz, an initial strain of 10%, and a dynamic strain of ±3%. The loss tangent tanδ of the first rubber layer 8a is preferably larger than the loss tangent tanδ of the topping rubber of the first belt ply 5a. The loss tangent tanδ of the first rubber layer 8a is preferably larger than the loss tangent tanδ of the tread rubber 3a. In order to suppress heat generation at the end of the belt 5, the loss tangent tanδ of the first rubber layer 8a is preferably 0.25 or less. The loss tangent tanδ of the first rubber layer 8a is not limited to the above, and may be 0.30 or less.

[0035] The communicating portion CP1 is provided at a position overlapping with the first rubber layer 8a in a plan view of the tread. That is, the communicating portion CP1 is provided between an axially inner end E2 (hereinafter simply referred to as the "inner end E2") of the first rubber layer 8a and an axially outer end E3 (hereinafter simply referred to as the "outer end E3") of the first rubber layer 8a in the tire axial direction. According to this configuration, by providing the first rubber layer 8a at a position overlapping with the communicating portion CP1, where vibrations tend to become relatively large during running, in a plan view of the tread, the vibrations transmitted from the communicating portion CP1 to the belt 5 can be absorbed by the first rubber layer 8a. This can suppress distortion of the belt 5 due to vibrations and suppress separation starting from the end of the belt 5. In addition, by suppressing distortion of the belt 5, the durability performance of the belt 5 can be improved.

[0036] In plan view of the tread, the communication portion CP1 is preferably 1 mm or more away from each of the axial ends E2, E3 of the first rubber layer 8a. That is, in plan view of the tread, the communication portion CP1 is preferably 1 mm or more away axially outward from the inner end E2 of the first rubber layer 8a and 1 mm or more away axially inward from the outer end E3 of the first rubber layer 8a. This configuration increases the absorption rate of vibration transmitted from the communication portion CP1 to the belt 5 by the first rubber layer 8a, and enhances the effect of suppressing separation by providing the first rubber layer 8a.

[0037] The first rubber layer 8a overlaps with the dimples 70 in a plan view of the tread. The overlap width OW therebetween is preferably 1 mm or more. The overlap width OW is preferably 1 mm or more smaller than the length L8 (see FIG. 4(A)) of the first rubber layer 8a in the tire axial direction. In one example, the overlap width OW is 5 mm.

[0038] As shown in FIG. 4(A), the first rubber layer 8a is preferably formed in a U-shaped cross section covering the outer end 5aE of the first belt ply 5a. That is, the outer end 5aE of the first belt ply 5a is preferably wrapped by the first rubber layer 8a. With this configuration, the vibration transmitted to the outer end 5aE of the first belt ply 5a is absorbed by the first rubber layer 8a, and the effect of suppressing separation starting from the end of the belt 5 can be enhanced. In this configuration, the inner end E2a of the first rubber layer 8a on the outer circumferential side (upper side in FIG. 4) is provided at substantially the same position in the tire axial direction as the inner end E2b of the first rubber layer 8a on the inner circumferential side (lower side in FIG. 4), but is not limited thereto. The first rubber layer 8a is not limited to the above, and may be provided only on the outer circumferential surface of the first belt ply 5a, as shown in FIG. 4(B). In FIG. 4, it appears as if a gap is generated between the first belt ply 5a and the second belt ply 5b, but in reality, no gap is generated due to deformation of the rubber layer 8 and the like.

[0039] The inner end E2 of the first rubber layer 8a is preferably disposed axially inward of the outer end 5bE of the second belt ply 5b. This allows the first rubber layer 8a to be interposed between the outer peripheral surface of the first belt ply 5a and the inner peripheral surface of the second belt ply 5b, and the first rubber layer 8a can absorb vibrations to suppress distortion between the belt plies 5a, 5b, and suppress separation between the belt plies 5a, 5b. It is more preferable that the first rubber layer 8a is provided up to the outer end 5aE of the first belt ply 5a. This allows the first rubber layer 8a to absorb vibrations transmitted to the outer end 5aE of the first belt ply 5a, and further suppress separation starting from the outer end 5aE of the first belt ply 5a.

[0040] As shown in Fig. 4(C), it is preferable that the second rubber layer 8b having a lower complex elastic modulus than the tread rubber 3a is provided on the outer peripheral surface and / or inner peripheral surface of the second belt ply 5b. With this configuration, the vibration transmitted from the communicating portion CP1 to the belt 5 is absorbed by the second rubber layer 8b, and the effect of suppressing separation starting from the end of the belt 5 can be enhanced. In particular, in a tire as disclosed herein that does not have a cap ply, separation starting from the end of the belt 5 can be effectively suppressed. This is because the belt 5 is easily distorted in a tire that does not have a cap ply.

[0041] The second rubber layer 8b may be formed of the same material as the first rubber layer 8a, or may be formed of a material different from that of the first rubber layer 8a. The second rubber layer 8b is preferably provided on the outer peripheral surface of the second belt ply 5b. This makes it possible to reduce the separation distance SD compared to when the second rubber layer 8b is provided on the inner peripheral surface of the second belt ply 5b, and to make it difficult for separation to occur between the belt plies 5a, 5b. It is more preferable that the second rubber layer 8b is provided up to the outer end 5bE of the second belt ply 5b. This allows the second rubber layer 8b to absorb vibrations transmitted to the outer end 5bE of the second belt ply 5b, and further suppresses separation starting from the end of the belt 5.

[0042] As shown in Fig. 4(D), the second rubber layer 8b may be formed in a U-shaped cross section covering the outer end 5bE of the second belt ply 5b. That is, the outer end 5bE of the second belt ply 5b may be wrapped by the second rubber layer 8b. As shown in Fig. 4(E), the second rubber layer 8b may be provided only on the inner peripheral surface of the second belt ply 5b.

[0043] 4(A) to 4(E), the first rubber layer 8a and the second rubber layer 8b may be combined in any desired manner. However, from the viewpoint of suppressing deterioration of rolling resistance due to an increase in tire mass and deterioration of separation suppression effect due to an increase in the mass (thickness) of the belt 5 ends, it is preferable that only one of the first rubber layer 8a and the second rubber layer 8b has a U-shaped cross section.

[0044] As shown in FIG. 3, among the multiple lands 20, the shoulder land 24 including the ground contact end TE includes a lug groove 33 extending in a direction intersecting the tire circumferential direction. In the tire meridian cross section shown in FIG. 3, the lug groove 33 included in the shoulder land 24 is drawn in a cross section along the groove width center line. The lug groove 33 has a tapered portion 33G in which the groove depth D33 gradually decreases toward the axially inner side of the tire (corresponding to the left side of FIG. 3), and a constant portion 33S that is connected to the axially outer side of the tapered portion 33G and extends with a substantially constant groove depth D33. The groove depth D33 of the lug groove 33 is a dimension along the normal direction of the tread surface 3f, and in this embodiment, it is maximum at the constant portion 33S.

[0045] The lug groove 33 has a tapered portion 33G and a constant portion 33S, so that the land rigidity of the shoulder land 24 is increased while the groove volume of the lug groove 33 is secured, and appropriate drainage performance can be achieved. Ensuring the land rigidity of the shoulder land 24 in the outer region OUT is useful for improving steering stability. From these viewpoints, it is preferable that the axially inner end E1 of the constant portion 33S (hereinafter simply referred to as the "inner end E1") is located axially outboard of the widthwise center position (the center position of the maximum width) of the shoulder land 24. The widthwise center position of the shoulder land 24 is determined as a position that is half the axial distance from the groove edge formed by the surface of the shoulder land 24 and the groove wall of the shoulder main groove 13 to the ground contact end TE.

[0046] The lug groove 33 extends from an opening end 33a that opens into the shoulder main groove 13 toward the axially outer side of the tire and crosses the ground contact edge TE. The lug groove 33 has a communication portion 33C that is interposed between the tapered portion 33G and the shoulder main groove 13 to communicate the two. The communication portion 33C extends with a groove depth at the axially inner end of the tapered portion 33G, and the groove depth is smaller than the groove depth of the constant portion 33S. In this embodiment, an example is shown in which the lug groove 33 is connected to the main groove 10 (specifically, the shoulder main groove 13), but this is not limited thereto, and the lug groove 33 may be separated from the main groove 10. In this case, the lug groove 33 has a closed end that is closed within the land instead of the opening end 33a.

[0047] If the first rubber layer 8a is disposed on the tire radially inner side of the tapered portion 33G where the rubber gauge Gr from the groove bottom of the lug groove 33 to the outer peripheral surface of the second belt ply 5b is relatively large, this is considered to be disadvantageous in suppressing heat generation, in combination with the fact that the thickness of the belt 5 is increased by the attachment of the first rubber layer 8a. Therefore, in this embodiment, the first rubber layer 8a is disposed on the tire axially outer side of the inner end E1 of the constant portion 33S. As a result, the first rubber layer 8a is disposed on the tire radially inner side of the constant portion 33S where the rubber gauge Gr is relatively small, rather than the tapered portion 33G where the rubber gauge Gr is relatively large. As a result, heat generation at the belt end can be appropriately suppressed, and the durability of the belt 5 can be effectively improved.

[0048] From the viewpoint of ensuring the heat generation suppression effect of the first rubber layer 8a, it is preferable that the inner end E2 of the first rubber layer 8a is separated from the inner end E1 of the constant portion 33S by a distance K of 5 mm or more outward in the tire axial direction. The first rubber layer 8a extends from the outer end 5aE toward the tire equator TC on the outer peripheral surface of the first belt ply 5a. It is preferable that the length L8 of the first rubber layer 8a in the tire axial direction (see FIG. 4(A)) is 10 mm or more. From the viewpoint of ensuring the length L8 of the first rubber layer 8a, it is considered to set the distance K to 7 mm or less, but is not limited thereto.

[0049] In this embodiment, as shown in Fig. 3, the profile of the tread surface 3f is formed of a plurality of arcs 90 curved to be convex toward the outside in the tire radial direction. The plurality of arcs 90 include a center arc 91 located on the tire equator TC, a quarter arc 92 connected to the center arc 91 on the outside in the tire axial direction, and a shoulder arc 93 connected to the quarter arc 92 on the outside in the tire axial direction. An inner end E2 of the first rubber layer 8a is disposed on the inside in the tire radial direction of the shoulder arc 93.

[0050] The center arc 91, the quarter arc 92, and the shoulder arc 93 all have centers radially inward of the tread surface 3f. In this embodiment, the center of the center arc 91 is located on a plane (so-called tire equatorial plane) that passes through the tire equator TC and extends in the tire radial direction. The radius of curvature R91 of the center arc 91, the radius of curvature R92 of the quarter arc 92, and the radius of curvature R93 of the shoulder arc 93 satisfy the relationship R91>R92>R93. The radius of curvature R93 of the shoulder arc 93 is, for example, 105 to 155 mm. The same is true on the opposite side (vehicle inner side) not shown in FIG. 3.

[0051] The configuration of the outer region OUT has been described with reference to Figures 3 and 4, but in this embodiment, a similar configuration is also applied to the inner region IN. That is, as shown in Figure 2, the tire T includes a dimple 80 having a communicating portion CP2 with the sipe 41 in the ground contact edge region of the inner region IN, and a first rubber layer having a lower complex elastic modulus than the tread rubber 3a is provided on at least the outer circumferential surface of the first belt ply in the inner region IN, and the communicating portion CP2 is provided at a position overlapping with the rubber layer in a plan view of the tread.

[0052] In this embodiment, the communication portion CP1 and the communication portion CP2 are provided at positions overlapping the first rubber layer in a plan view of the tread, but are not limited thereto. At least one of the communication portion CP1 and the communication portion CP2 may be provided at a position overlapping the first rubber layer in a plan view of the tread.

[0053] The communication portion CP1 is provided at a position shifted in the tire circumferential direction from the communication portion CP2, that is, the communication portion CP1 is provided at a position not overlapping with the communication portion CP2 when viewed in the tire axial direction.

[0054] [Tread pattern details] The details of the tread pattern of the tire T of this embodiment will be described with reference to Fig. 2 and Figs. 5 to 9. However, the tread pattern of the tire of the present disclosure is not particularly limited as long as the communicating portion CP1 is formed in the ground contact edge region EA.

[0055] Outer Realm Quarter Land As shown in FIGS. 5 and 6, the quarter land 23 includes a sipe 44 and a shallow groove 50 formed shallower than the sipe 44. The sipe 44 has an opening end 44a that opens into the main groove 10 (specifically, the shoulder main groove 13) and a closed end 44b that closes within the land. That is, the sipe 44 has a semi-closed structure that opens into the shoulder main groove 13. The shallow groove 50 extends so as to surround the sipe 44 in a plan view of the tread, and is connected to the main groove 10 to which the opening end 44a opens. Such sipes 44 and the shallow grooves 50 surrounding them are repeatedly formed in the tire circumferential direction. The shallow groove 50 is connected only to the main groove 13 of the pair of main grooves 12, 13 that define the quarter land 23, and is not connected to the main groove 12. The shallow groove 50 is not connected to the lug grooves 30 or the sipes 40.

[0056] The sipes 44 can remove water by taking in water from the main grooves 13, but by providing the shallow grooves 50 as described above, the surrounding water flowing along the sipes 44 can be further taken in to enhance the water removal effect, which in turn improves drainage and steering stability on wet road surfaces. In addition, the shallow grooves 50 increase the flexibility of the periphery of the edges of the sipes 44, making them more likely to fit the road surface (improving ground contact), which is convenient for ensuring steering stability on wet road surfaces and can contribute to improving braking performance on wet road surfaces. However, if the periphery of the edges of the sipes 44 moves too much, there is a risk that the ground contact will worsen, so the shallow grooves 50 are formed shallower than the sipes 44.

[0057] As shown in FIG. 7, in this embodiment, the depth of the sipe 44 changes in the extension direction. The sipe 44 has a base portion extending from the open end 44a to the closed end 44b with a relatively large depth D44a, a tip portion extending from the closed end 44b to the open end 44a with a relatively small depth D44b, and an intermediate portion whose depth gradually changes so as to connect them. In one example, the depth D44a is 6.5 mm, and the depth D44b is 3 mm. In this embodiment, the groove depth D50 of the shallow groove 50 (see FIG. 8) is set smaller than the minimum depth D44b of the sipe 44, but may be set smaller than the maximum depth D44a of the sipe 44.

[0058] 8 is a cross-sectional view taken along the line XX in FIG. 5. From the viewpoint of enhancing the water removal effect of the sipe 44, it is preferable that the sipe 44 has a width W44 of 1.0 mm or more. It is preferable that the sipe 44 is formed wider than other sipes 40 that are not surrounded by the shallow groove 50, for example, the sipe 43 formed in the same quarter land 23. In one example, the width of the sipe 43 is 0.6 mm, while the width W44 of the sipe 44 is 1.5 mm. The sipe 44 is formed as a two-dimensional sipe whose shape does not change along the depth direction, but is not limited thereto, and may be a three-dimensional sipe including a portion whose shape changes along the depth direction.

[0059] In this embodiment, the shallow groove 50 extends with a constant groove depth D50. In order to ensure the improvement effect of the shallow groove 50, the groove depth D50 is preferably 0.8 mm or more. In order to suppress deterioration of ground contact, the groove depth D50 is preferably 1.5 mm or less. The groove width W50 of the shallow groove 50 is, for example, 0.5 to 1.0 mm. The groove width W50 is smaller than the width W44 of the sipe 44, but is not limited to this. The contour of the groove edge 50E formed by the surface of the land 20 and the groove wall of the shallow groove 50 is formed by a circular arc, which can reduce the edge pressure. The curvature radius R of this circular arc is, for example, 0.3 mm or more. In one example, the groove depth D50 is 1.0 mm, the groove width W50 is 0.8 mm, and the curvature radius R is 0.3 mm.

[0060] In order to ensure the improvement effect of the shallow groove 50, the interval G1 between the sipe 44 and the shallow groove 50 in the width direction of the sipe 44 is preferably 1.5 mm or less, more preferably 1.0 mm or less. In addition, from the viewpoint of suppressing deterioration of ground contact, the interval G1 is preferably 0.8 mm or more. In one example, the interval G1 is 1.0 mm. In this embodiment, the interval G1 is substantially constant except for the acute angle portion formed by the sipe 44 and the shoulder main groove 13. In the acute angle portion, the shallow groove 50 is away from the sipe 44 so as not to interfere with the shelf 23s (or chamfer) described later. The interval G2 (see FIG. 5) between the closed end 44b and the shallow groove 50 in the extension direction of the sipe 44, measured along the width center line of the sipe 44, is, for example, 5.0 to 10.0 mm.

[0061] The sipes 44 and the shallow grooves 50 surrounding the sipes 44 may be included in at least one land 20. As described above, in this embodiment, an example is shown in which they are included in the quarter land 23. Since the sipes 44 and the shallow grooves 50 that open toward the tire axially outward are included in the quarter land 23, the drainage performance in the shoulder main groove 13 can be improved. However, this is not limited to this, and such sipes 44 and shallow grooves 50 may be connected to the center main groove 12. In addition, the sipes 44 and shallow grooves 50 may be included in the shoulder lands 21, 24 or the center land 25 described later.

[0062] In this embodiment, the land 20 including the sipes 44 and the shallow grooves 50 (i.e., the quarter land 23) is provided as a rib that extends continuously in the tire circumferential direction. In this embodiment, the quarter land 23 does not include a lug groove 30. Since the quarter land 23 is a rib, the decrease in land rigidity is suppressed even though the sipes 44 and the shallow grooves 50 are included, which is convenient in terms of ensuring steering stability. However, without being limited thereto, the land including such sipes 44 and the shallow grooves 50 may be a block row in which a plurality of blocks are arranged in the tire circumferential direction.

[0063] In this embodiment, an example is shown in which the sipes 44 and shallow grooves 50 are provided in the outer region OUT. By improving drainage by the sipes 44 and shallow grooves 50 instead of the lug grooves 30, the decrease in land stiffness in the outer region OUT is suppressed, which is convenient for ensuring steering stability. In addition, by opening the sipes 44 and shallow grooves 50 to the main groove 10, the contact length along the tire circumferential direction is lengthened and the contact pressure is reduced, making it easier to ensure the contact performance of the outer region OUT. However, this is not limited to this, and such sipes 44 and shallow grooves 50 may be provided in the inner region IN.

[0064] 5 and 6, the shallow groove 50 has a first groove portion 51 spaced from the sipe 44 on one side in the tire circumferential direction, a second groove portion 52 spaced from the sipe 44 on the other side in the tire circumferential direction, and a third groove portion 53 spaced from the closed end 44b in the extension direction of the sipe 44. The first groove portion 51 and the second groove portion 52 each open to the main groove 13. Since a shelf 13s is formed on the groove edge formed by the groove wall of the main groove 13 and the surface of the land 20, water is easily taken in from the main groove 13 to the sipe 44 and the shallow groove 50. The width of the shelf 13s is, for example, 0.3 to 1.0 mm. The depth of the shelf 13s is, for example, 0.5 to 1.5 mm. It is preferable that the depth of the shelf 13s is equal to or greater than the groove depth D50 of the shallow groove 50.

[0065] The shallow groove 50 has partition walls 54 provided between the first groove portion 51 and the third groove portion 53 and between the second groove portion 52 and the third groove portion 53. The shallow groove 50 is formed by a protrusion provided on the tire molding surface of a mold used for vulcanization molding of the tire T, and the protrusion has a shape divided at a position corresponding to the partition wall 54. A tire molding surface including a protrusion is generally made by casting an aluminum material. By dividing the protrusion to shorten its length, waving of the protrusion due to shrinkage during casting is suppressed, and the shallow groove 50 can be appropriately formed. In addition, the divided portion of the protrusion functions as a bypass through which air can pass when vulcanizing the tire T, which helps to reduce vulcanization molding defects.

[0066] The shallow groove 50 does not have a groove portion that is bent in a plan view of the tread by having the partition wall 54. The first groove portion 51, the second groove portion 52, and the third groove portion 53 are not bent in a plan view of the tread, and are formed in a simple straight or curved shape. This can suppress the retention of air in the shallow groove 50, and contribute to the reduction of air columnar resonance noise. The thickness T54 of the partition wall 54 is, for example, 0.5 to 1.0 mm. In one example, the thickness T54 is 0.8 mm. The partition wall 54 extends in the extension direction of the third groove portion 53, but is not limited thereto, and may extend in the extension direction of the first groove portion 51 or the second groove portion 52, for example. The shallow groove 50 may have a structure that does not have the partition wall 54.

[0067] In this embodiment, the sipe 44 extends in a curved manner while gradually increasing the angle with respect to the tire circumferential direction from the closed end 44b toward the open end 44a. With this configuration, the sipe 44 is connected to the main groove 13 at an appropriate angle, and the edges of the sipe 44 are prevented from contacting the ground all at once when the tire T rolls, thereby reducing pattern noise. The sipe 44 has a shape in which a plurality of arcs with different radii of curvature are connected in a plan view of the tread. The tip portion of the sipe 44 including the closed end 44b is composed of an arc with a relatively small radius of curvature, and the main portion of the sipe 44 including the open end 44a is composed of an arc with a relatively large radius of curvature. However, this is not limited to this, and the sipe 44 may be composed of a single arc.

[0068] The first groove portion 51 and the second groove portion 52 are curved along the sipe 44. The first groove portion 51 located on the outer circumferential side of the curve of the sipe 44 extends in the tire circumferential direction beyond the closed end 44b of the sipe 44, and the third groove portion 53 extends at an angle with respect to the tire axial direction. The sipe 44 is not limited to a curved shape, and may be, for example, a linearly extending shape. The first groove portion 51 and the second groove portion 52 preferably have a shape following the sipe 44 in a plan view of the tread, but are not limited thereto. However, it is preferable that the above-mentioned interval G1 is within a range of 0.8 to 1.5 mm so that the shallow groove 50 is neither close nor far from the sipe 44.

[0069] In this embodiment, a shelf 23s is provided at the acute angle portion formed by the sipe 44 and the shoulder main groove 13. This makes it possible to suppress heel-and-toe wear in which the acute angle portion with low rigidity wears preferentially. The depth of the shelf 23s is, for example, 1.5 to 3.0 mm. The depth of the shelf 23s is set to be greater than or equal to the depth of the shelf 13s. The shelf 23s is formed in a triangular shape in a plan view of the tread. The acute angle portion may be provided with a chamfer (not shown) instead of the shelf 23s. The chamfer is formed, for example, by an inclined surface whose depth gradually increases toward the tip of the acute angle portion.

[0070] In the quarter land 23, the sipes 43 and sipes 44 are arranged alternately along the tire circumferential direction, and overlap when viewed in the tire circumferential direction. The sipes 43 have a semi-closed structure that opens into the center main groove 12. The sipes 43 extend at an incline with respect to the tire axial direction. The sipes 43 are inclined in the same direction as the main portions of the sipes 44 and the third groove portion 53. In addition, the quarter land 23 is provided with dimples 60. The dimples 60 are arranged between the sipes 43 and the shallow grooves 50 (the first groove portions 51). By providing the dimples 60, the rigidity difference in the quarter land 23 can be reduced, improving the rigidity balance.

[0071] The depth of the dimples 60 is preferably equal to the depth of the tips of the sipes 44 (depth D44b described above), and more specifically, the ratio of the relatively small depths to the relatively large depths is preferably 80% or more, and more preferably 90% or more. With this configuration, the tips of the sipes 44 and the dimples 60 wear away at approximately the same time, making the apparent uneven wear less noticeable. The dimples 60 have a shape that tapers along the extension direction of the sipes 44 in a plan view of the tread. This reduces the groove volume of the dimples 60, and suppresses pattern noise caused by the dimples 60.

[0072] Inner Realm Quarter Land As shown in FIG. 9, the quarter land 22 and the quarter land 23 are adjacent to each other in the tire axial direction with one center main groove 12 between them. The quarter land 22 includes a lug groove 32 and a sipe 42. The lug groove 32 has a semi-closed structure that opens to the shoulder main groove 11. That is, the lug groove 32 has an open end 32a that opens to the shoulder main groove 11 and a closed end 32b that closes within the land. The sipe 42 has a semi-closed structure that opens to the center main groove 12. That is, the sipe 42 has an open end 42a that opens to the center main groove 12 and a closed end 42b that closes within the land. The lug grooves 32 and the sipes 42 are alternately arranged in the tire circumferential direction, and they overlap when viewed in the tire circumferential direction.

[0073] In the quarter land 22, the lug grooves 32 and the sipes 42 are arranged in a staggered pattern in the tire circumferential direction, which can contribute to the uniformization of land stiffness (rib stiffness) and the suppression of uneven wear (the amount of wear on the axially outer side of the quarter land 22 is greater than that on the axially inner side of the tire). From the viewpoint of the uniformization of land stiffness, it is preferable that the interval G22 between the lug groove 32 and the sipe 42 at the width center position (the center position of the maximum width) of the quarter land 22 is substantially constant. Specifically, it is preferable that the minimum value of the interval G22 is 90% or more of the maximum value, and more preferably 95% or more. The lug grooves 32 opening to the shoulder main grooves 11 formed in the quarter land 22 are useful for ensuring drainage in the shoulder main grooves 11 that are not connected to the lug grooves 31.

[0074] The lug grooves 32 are tapered toward the closed end 32b. This makes it easy to ensure the land stiffness of the portion of the quarter land 22 on the tire equator TC side while suppressing abrupt changes in land stiffness. The same is true for the lug grooves 31 included in the shoulder land 21. The lug grooves 32 are connected only to the shoulder main grooves 11, and are not connected to other lug grooves 30 or sipes 40. The sipes 42 are connected only to the center main groove 12, and are not connected to other lug grooves 30 or sipes 40. Only the lug grooves 32 and the sipes 42 are formed in the quarter land 22.

[0075] The lug grooves 32 are curved so as to be convex in the tire circumferential direction. The lug grooves 32 are curved so as to be convex downward in Fig. 9. The center of the arc passing through the groove width center of the lug groove 32 is located on one side of the lug groove 32 in the tire circumferential direction (upper side in Fig. 9). The sipes 42 are curved so as to be convex in the same direction as the lug grooves 32 in the tire circumferential direction. With this configuration, it is possible to uniform the land stiffness of the quarter land 22 by suppressing a sudden change in the interval between the lug grooves 32 and the sipes 42 in the tire axial direction.

[0076] The sipe 42 is smoothly connected to the sipe 43 through the main groove 10 (specifically, the center main groove 12). According to this configuration, the sipes 42 and 43 are appropriately misaligned in the tire circumferential direction, which is convenient for suppressing pattern noise. The smooth connection of two sipes 40 (or lug grooves 30) through the main groove 10 refers to a state in which a virtual line extending one of the sipes in the length direction and a virtual line extending the other in the length direction overlap in the main groove 10 or are close to each other such that the distance between them in the tire circumferential direction is 10.0 mm or less. In the example of FIG. 9, the virtual lines L42 and L43 passing through the width centers of the sipes 42 and 43 are close to each other in the main groove 10.

[0077] Shoulder Land The shoulder land 21 includes a lug groove 31 and a sipe 41. The lug groove 31 is separated from the main groove 10 and does not communicate with the shoulder main groove 11. The lug groove 31 extends from a closed end 31a that is closed within the land to the tire axially outward and crosses the ground contact end TE. The shoulder land 21 is not completely divided by the lug groove 31. The shoulder land 21 is formed as a rib that extends continuously in the tire circumferential direction. The sipe 41 extends from an opening end 41a that opens into the shoulder main groove 11 to the tire axially outward and crosses the ground contact end TE. No sipes 40 other than the sipe 41 are formed in the shoulder land 21. The lug grooves 31 and the sipes 41 are alternately arranged in the tire circumferential direction.

[0078] The lug grooves 31 are curved so as to be convex in the tire circumferential direction. The lug grooves 31 are curved so as to be convex downward in FIG. 9. The center of the arc passing through the groove width center of the lug groove 31 is located on one side of the lug groove 31 in the tire circumferential direction (upper side in FIG. 9). The lug grooves 31 are curved so as to be convex in the same direction as the lug grooves 32 in the tire circumferential direction. The sipes 41 are curved so as to be convex in the same direction as the lug grooves 31 in the tire circumferential direction. With this configuration, it is possible to uniformize the land stiffness of the shoulder land 21 by suppressing a sudden change in the interval between the lug grooves 31 and the sipes 41 in the tire axial direction. The sipes 41 are curved so as to be convex in the same direction as the sipes 42 in the tire circumferential direction.

[0079] The lug groove 31 smoothly continues to the lug groove 32 via the main groove 10 (specifically, the shoulder main groove 11). According to this configuration, the lug groove 31 and the lug groove 32 are appropriately misaligned in the tire circumferential direction, which is convenient for suppressing pattern noise. In the example of FIG. 9, the imaginary lines L31 and L32 passing through the groove width centers of the lug grooves 31 and 32 overlap in the main groove 10. The sipe 41 smoothly continues to the sipe 42 via the main groove 10 (specifically, the shoulder main groove 11). According to this configuration, the sipe 41 and the sipe 42 are appropriately misaligned in the tire circumferential direction, which is convenient for suppressing pattern noise. In the example of FIG. 9, the imaginary lines L41 and L42 passing through the width centers of the sipes 41 and 42 overlap in the main groove 10.

[0080] From the viewpoint of suppressing uneven wear of the shoulder land 21 (increasing the difference in the amount of wear between the axially outer side and the axially inner side of the shoulder land 21), it is preferable that the interval G21 between the lug groove 31 and the sipe 41 at the widthwise center position (the center position of the maximum width) of the shoulder land 21 is substantially constant. Specifically, it is preferable that the minimum value of the interval G21 is 85% or more of the maximum value, and more preferably 90% or more. The widthwise center position of the shoulder land 21 is determined as a position that is half the distance in the axial direction of the tire from the groove edge formed by the surface of the shoulder land 21 and the groove wall of the shoulder main groove 11 to the ground contact edge TE.

[0081] As shown in FIG. 2, the shoulder land 24 includes the lug groove 33 and the sipe 45 described above. The lug groove 33 extends from an opening end 33a (see FIG. 3) that opens into the shoulder main groove 13 toward the outside in the tire axial direction and crosses the ground contact edge TE. The lug groove 33 is curved so as to be convex in the same direction as the sipe 44 in the tire circumferential direction. The center of the arc passing through the groove width center of the lug groove 33 is located on the other side of the lug groove 33 in the tire circumferential direction (the lower side in FIG. 2). The lug groove 33 smoothly continues to the sipe 44 via the main groove 10 (specifically, the shoulder main groove 13). The sipe 45 is separated from the shoulder main groove 13 and connected to the lug groove 33. The lug groove 33 and the sipe 45 are alternately arranged in the tire circumferential direction. The sipe 45 is curved so as to be convex in the opposite direction to the lug groove 33 in the tire circumferential direction.

[0082] As shown in FIG. 2, in this embodiment, at least in the region SA on the axially inner side of the tire tread edge TE, the sipes 41 and 45 are misaligned in the tire circumferential direction so that the imaginary line VL parallel to the tire axial direction intersecting the sipe 41 does not intersect with the sipe 45. FIG. 2 shows two imaginary lines VL. One of them passes through the opening end 41a of the sipe 41, and the other passes through the intersection of the sipe 41 and the tread edge TE. If the imaginary line VL intersects with the sipe 41 in the region SA, it will not intersect with the sipe 45 no matter where it is set. In other words, the sipes 41 and 45 in the region SA do not overlap each other when viewed in the tire axial direction.

[0083] In this embodiment, the sipes 41 included in the shoulder land 21 and the sipes 45 included in the shoulder land 24 are curved so as to be convex in the same circumferential direction of the tire, but as described above, they are misaligned in the circumferential direction of the tire. This makes it possible to suppress pattern noise caused by the sipes 41 and 45. In addition, in this embodiment, the lug grooves 33 included in the shoulder land 24 in the outer region OUT are curved as described later, and the sipes 45 are curved so as to be convex in the opposite direction to the lug grooves 33 in the circumferential direction of the tire. Therefore, the frequency of the pitch noise is more easily dispersed than when they are curved in the same direction, and pitch noise during steering is suppressed.

[0084] It is preferable that the radius of curvature SR1 of the sipe 41 is different from the radius of curvature SR2 of the sipe 45. As a result, one sipe (sipe 41 in this embodiment) is curved relatively less and closer to a straight line, while the other sipe (sipe 45 in this embodiment) is curved relatively more. By making the curvatures different in this way in addition to the circumferential positional deviation of the tire, pattern noise caused by the sipes 41 and 45 can be effectively suppressed. The difference between the radius of curvature SR1 and the radius of curvature SR2 is, for example, 60 mm or more. The radii of curvature SR1 and SR2 are calculated as the radius of curvature of an arc passing through the center of the width of the sipes 41 and 45 in the region SA, respectively.

[0085] In this embodiment, the radius of curvature SR2 of the sipe 45 located on the outer side of the vehicle when installed on the vehicle is smaller than the radius of curvature SR1 of the sipe 41 located on the inner side of the vehicle when installed on the vehicle (SR1>SR2). As a result, the angle of the sipe 45 provided in the outer region OUT to the tire circumferential direction is large at the axially outer portion thereof, thereby suppressing uneven wear.

[0086] In this embodiment, the sipes 41 located on the inside of the vehicle when the tire is installed on the vehicle are connected to the main groove 10 (i.e., the shoulder main groove 11), and the sipes 45 located on the outside of the vehicle when the tire is installed on the vehicle are separated from the main groove 10. As a result, in the shoulder land 21 of the inside region IN, the sipes 41 can also remove water by taking in water from the shoulder main groove 11, improving drainage. Since the lug grooves 31 do not communicate with the main groove 10, such a sipe 41 structure is even more beneficial. Also, in the shoulder land 24 of the outside region OUT, the decrease in land rigidity due to the sipes 45 is suppressed, which is advantageous in ensuring steering stability during cornering.

[0087] The sipes 41 extend across the ground contact edge TE and are connected to a dimple 80 formed axially outward of the ground contact edge TE. This increases flexibility of the area between the adjacent lug grooves 31, improving ground contact at the shoulder land 21. The width and depth of the dimples 80 are substantially the same as those of the dimples 70.

[0088] The dimple 80 is formed in a crescent shape that is relatively narrow at both ends in the tire axial direction and relatively wide at the center, but is not limited to this. The dimple 80 is curved so as to be convex in the same direction as the sipes 41 in the tire circumferential direction. In this embodiment, the dimple 80 is curved so as to be convex in the same direction as the dimple 70 in the tire circumferential direction, and is shorter in the tire axial direction than the dimple 70, but is not limited to this.

[0089] In this embodiment, the first connecting body 71 and the second connecting body 81 are shifted in the tire circumferential direction so that the imaginary line VL' parallel to the tire axial direction intersecting with the first connecting body 71 formed by the sipe 45 and the dimple 70 does not intersect with the second connecting body 81 formed by the sipe 41 and the dimple 80. This makes it possible to more effectively suppress pattern noise caused by the sipes 41 and 45. The imaginary line VL' intersecting with the first connecting body 71 will not intersect with the second connecting body 81 no matter where it is set. In other words, the first connecting body 71 and the second connecting body 81 do not overlap each other when viewed in the tire axial direction.

[0090] [Variations in tread pattern] In the above embodiment, an example in which three main grooves 10 are provided on the tread surface 3f has been shown, but the number of main grooves 10 is not limited to this, and may be two, four, five or more. FIG. 2 shows an example in which four main grooves are provided on the tread surface 3f, thereby partitioning five lands 20. The four main grooves 10 include a pair of shoulder main grooves 11, 13 and a pair of center main grooves 12, 14 located between them. The five lands 20 include a pair of shoulder lands 21, 24, a pair of quarter lands 22, 23, and a center land 25 formed between the pair of center main grooves 12, 14. The center land 25 is provided on the tire equator TC. The center land 25 has lug grooves 34 and lug grooves 35 arranged in a staggered manner along the tire circumferential direction.

[0091] The tire T of the present embodiment is the same as a normal pneumatic tire except that the communicating portion and the rubber layer are configured as described above, and any of the conventionally known materials, shapes, structures, etc. can be adopted.

[0092] [1] As described above, the tire T of the present embodiment includes the sipes 45 provided on the tread surface 3f, the dimples 70 having a communicating portion CP1 with the sipes 45 in the ground contact edge region EA, and the belt 5 laminated on the tire radial outer side of the carcass 4, the belt 5 including the first belt ply 5a having the widest width in the tire axial direction among the multiple belt plies constituting the belt 5, and the second belt ply 5b laminated on the tire radial outer side of the first belt ply 5a and having no other member interposed between it and the tread rubber 3a, the first rubber layer 8a having a complex elastic modulus lower than that of the tread rubber 3a is provided on at least the outer peripheral surface of the first belt ply 5a, and the communicating portion CP1 is provided at a position overlapping with the first rubber layer 8a in a plan view of the tread.

[0093] According to this configuration, by providing the first rubber layer 8a at a position overlapping the communicating part CP1, where vibrations tend to become relatively large during running, in a plan view of the tread, the first rubber layer 8a can absorb vibrations transmitted from the communicating part CP1 to the belt 5. This makes it possible to suppress distortion of the belt 5 due to vibrations and to suppress separation starting from the end of the belt 5.

[0094] [2] In the tire T of [1] above, it is preferable that the communication portion CP1 is spaced 1 mm or more from each of both axial ends E2, E3 of the first rubber layer 8a in a plan view of the tread.

[0095] According to this configuration, the absorption rate of the vibration transmitted from the communication part CP1 to the belt 5 by the first rubber layer 8a can be increased, and the effect of suppressing separation by providing the first rubber layer 8a can be enhanced.

[0096] [3] In the tire T according to the above [1] or [2], the first rubber layer 8a is preferably formed in a U-shaped cross section covering the axially outer end of the first belt ply 5a.

[0097] According to this configuration, the vibration transmitted to the outer end 5aE of the first belt ply 5a is absorbed by the first rubber layer 8a, and the effect of suppressing separation starting from the end of the belt 5 can be enhanced.

[0098] [4] In the tire T of any one of the above [1] to [3], it is preferable that a second rubber layer 8b having a complex modulus lower than that of the tread rubber 3a is provided on an outer circumferential surface and / or an inner circumferential surface of the second belt ply 5b.

[0099] According to this configuration, the vibration transmitted from the communicating portion CP1 to the belt 5 is absorbed by the second rubber layer 8b, and the effect of suppressing separation starting from the end of the belt 5 can be enhanced.

[0100] Although the embodiment of the present disclosure 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 disclosure is indicated not only by the description of the above embodiment but also by the claims, and further includes all modifications within the meaning and scope equivalent to the claims.

[0101] The tire of the present disclosure is not limited to the above-mentioned embodiment, and is not limited to the above-mentioned action and effect. The tire of the present disclosure can be variously improved or modified without departing from the spirit of the tire. In addition, the configurations adopted in the above-mentioned embodiment can be adopted in any combination. [Explanation of symbols]

[0102] T Tire 3a Tread Rubber 3f Tread surface 4. Carcass 5 Belt 5a 1st belt ply 5b 2nd belt ply 6 Cap Ply 8a First rubber layer 8b Second rubber layer 41,45 Sipe 70,80 dimples CP1,CP2 communication part

Claims

1. Sipes provided on the tread surface; a dimple having a communicating portion with the sipe in a ground contact edge region; A belt is laminated on the outer side of the carcass in the tire radial direction, The belt includes a first belt ply having a widest width in the tire axial direction among a plurality of belt plies constituting the belt, and a second belt ply laminated on the tire radial direction outer side of the first belt ply and having no other member interposed between the second belt ply and a tread rubber, A first rubber layer having a complex elastic modulus lower than that of the tread rubber is provided on at least an outer peripheral surface of the first belt ply, the communicating portion is provided at a position overlapping the first rubber layer in a plan view of the tread.

2. The tire according to claim 1 , wherein the communication portion is spaced from each of both ends in the tire axial direction of the first rubber layer by 1 mm or more when viewed in the tire radial direction.

3. The tire according to claim 1 , wherein the first rubber layer is formed in a U-shaped cross section covering an axially outer end of the first belt ply.

4. The tire according to any one of claims 1 to 3, wherein a second rubber layer having a complex modulus lower than that of the tread rubber is provided on an outer peripheral surface and / or an inner peripheral surface of the second belt ply.

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