Pneumatic tire for heavy load

Abstract

To provide a pneumatic tire 2 for a heavy load which suppresses occurrence of uneven wear in a shoulder part of a tread and occurrence of TGC in a shoulder circumferential groove, without increasing tire weight.SOLUTION: A tire 2 has a call with a flat ratio of 70% or more. The tire 2 includes a tread 4 having a shoulder circumferential groove 28s, and a reinforcement layer 20. The reinforcement layer 20 includes a belt 38 and a band 60. The belt 38 includes main belts 40 having both ends opposite to each other while sandwiching an equatorial plane, and a pair of sub belts 48 which is arranged so as to be separated from one another in an axial direction. The main belt 40 includes one or more and three or less main belt plies 42. The sub belts 48 are provided at positions overlapped with the shoulder circumferential groove 28s in a radial direction, and both ends of the sub belts 48 are not overlapped with the shoulder circumferential groove 28s. A belt cord 44 included in the sub belts 48 is inclined by 20° or more with respect to the circumferential direction.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a heavy duty pneumatic tire. [Background technology]

[0002] A band having a jointless structure is often adopted to suppress the dimensional growth of the tire tread and ensure an appropriate ground contact shape of the tread surface, particularly in low-profile tires (tires with a nominal aspect ratio of 65% or less) that have a high internal tread pressure distribution rate (see, for example, Patent Document 1). On the other hand, for coach tires that require high resistance to uneven wear, bands with a jointless structure may be used even for high aspect ratio tires such as tires with a nominal aspect ratio of 70% or 80%. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2022-047999 Summary of the Invention [Problem to be solved by the invention]

[0004] High aspect tires are more susceptible to bending at the side portions than low aspect tires, and are therefore more susceptible to loss due to deformation during running, which leads to an increase in rolling resistance. Therefore, for example, in the heavy-duty pneumatic tire described in Patent Document 1, if a reinforcing layer having a belt composed of four belt plies arranged in the radial direction and a band composed of a full band and an edge band is adopted as the reinforcing layer, the full band can increase the binding force in the tire circumferential direction. Therefore, it is expected that the loss due to deformation during running will be reduced and the deterioration of rolling resistance will be prevented. On the other hand, when the reinforcing layer described in Patent Document 1 is used, the tire weight increases, and therefore the rolling resistance of the tire as a whole cannot be suppressed as much as expected.

[0005] Therefore, we considered reducing the number of belt plies, which is expected to reduce the rolling resistance of the entire tire by increasing the tire circumferential binding force while suppressing the increase in tire weight. However, if the number of belt plies is reduced, the rigidity in the width direction of the tread is expected to decrease. In particular, the rigidity in the axial direction around the shoulder circumferential groove is expected to decrease. Therefore, there is a concern that TGC (tread groove crack) may occur due to bending of the shoulder circumferential groove in the width direction.

[0006] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a heavy-duty pneumatic tire that ensures good resistance to uneven wear, suppresses an increase in tire weight, and inhibits the occurrence of TGC in shoulder circumferential grooves. [Means for solving the problem]

[0007] (1) A heavy-duty pneumatic tire according to one aspect of the present invention comprises: The nominal aspect ratio is 70% or more. The tire has a tread that comes into contact with a road surface, and a reinforcing layer that is located radially inside the tread, At least two circumferential grooves are cut into the tread to form at least three land portions arranged in parallel in the axial direction, and the circumferential groove located on the outer side in the axial direction of the at least two circumferential grooves is a shoulder circumferential groove, and the land portion located on the outer side of the shoulder circumferential groove in the axial direction is a shoulder land portion, The reinforcing layer includes a belt including a large number of parallel belt cords, and a band including a spirally wound band cord and having opposite ends facing each other across an equator plane, The belt includes a main belt having opposite ends sandwiching an equatorial plane, and a pair of sub-belts arranged apart from each other in an axial direction so as to sandwich the equatorial plane, The main belt includes one to three main belt plies arranged in a radial direction, The sub-belt is provided at a position overlapping the shoulder circumferential groove in the radial direction, while both ends of the sub-belt do not overlap the shoulder circumferential groove, The belt cord included in the sub-belt is inclined at an angle of 20° or more with respect to the circumferential direction. Heavy duty pneumatic tires.

[0008] This heavy-duty pneumatic tire is a highly flat tire that includes a spirally wound band cord and has a band with opposite ends on either side of the equatorial plane, so that the dimensional growth in the tread is nearly uniform and the tire has excellent resistance to uneven wear. This heavy-duty pneumatic tire is not heavy in weight because the number of main belt plies is three or less. This heavy-duty pneumatic tire is provided with a sub-belt including many parallel belt cords on the radially inner side of the shoulder circumferential groove, and the belt cords are inclined at 20° or more with respect to the circumferential direction. In other words, the belt cords are inclined at 20° or more with respect to the equatorial plane of the tire. Therefore, axial bending of the shoulder circumferential groove and dimensional growth of the shoulder portion of the tread are suppressed.

[0009] (2) In the heavy-duty pneumatic tire according to (1) above, the angle of the belt cord included in the sub-belt with respect to the circumferential direction is preferably equal to or greater than 30° and equal to or less than 80°.

[0010] (3) In the heavy duty pneumatic tire according to (2) above, the angle of the belt cord included in the sub-belt with respect to the circumferential direction is preferably equal to or greater than 30° and equal to or less than 50°.

[0011] (4) In the heavy duty pneumatic tire of (2) above, the angle of the belt cord included in the sub-belt with respect to the circumferential direction is preferably equal to or greater than 50° and equal to or less than 80°.

[0012] (5) In the heavy duty pneumatic tire of any one of (1) to (4) above, preferably, an outer end of the sub-belt is axially positioned inside an end of the main belt ply that is positioned radially outermost.

[0013] (6) In any of the heavy-duty pneumatic tires (1) to (5) above, an outer end of the sub-belt is preferably located axially inwardly of an end of the main belt ply that is located radially outermost, by 5 mm or more.

[0014] (7) Any of the heavy-duty pneumatic tires (1) to (6) above preferably has At least three circumferential grooves are formed in the tread, a crown circumferential groove is a circumferential groove located more inwardly than the shoulder circumferential groove in the axial direction, a land portion sandwiched between the shoulder circumferential groove and the crown circumferential groove in the axial direction is a middle land portion, The axial distance between the outer end of the sub-belt and the outer edge of the shoulder circumferential groove, and the axial distance between the inner end of the sub-belt and the inner edge of the shoulder circumferential groove are each 50% or more of the opening width of the shoulder circumferential groove; and The inner end of the sub-belt is located axially outboard of a midpoint of the middle land portion in the axial direction.

[0015] (8) Any of the heavy-duty pneumatic tires (1) to (7) above preferably has The axial distance between the shoulder circumferential groove and the equatorial plane is 45% or more and 75% or less of half the axial width of the tread.

[0016] (9) Any of the heavy-duty pneumatic tires (1) to (8) above preferably has a groove bottom shape of the shoulder circumferential groove in a meridian cross section is a shape formed by a circular arc, The radius of the arc is 2.5 mm or more.

[0017] (10) Any of the heavy-duty pneumatic tires (1) to (9) above preferably has The shortest distance between the shoulder circumferential groove and the sub-belt located radially inside the shoulder circumferential groove is 0.5 to 1.5 times the groove bottom width of the shoulder circumferential groove.

[0018] (11) Any of the heavy-duty pneumatic tires (1) to (10) above preferably has At least three circumferential grooves are formed in the tread, a crown circumferential groove is a circumferential groove located more inwardly than the shoulder circumferential groove in the axial direction, The groove bottom width of the crown circumferential groove is 0.5 times or less the opening width of the crown circumferential groove.

[0019] (12) In the heavy load pneumatic tire of (11) above, the groove bottom width of the crown circumferential groove is preferably 1 mm or more and 5 mm or less.

[0020] (13) In the heavy load pneumatic tire according to (11) above, the crown circumferential groove preferably has a groove bottom width of 2 mm or more and 3 mm or less.

[0021] (14) In the heavy load pneumatic tire of any of (7) and (11) to (13), preferably, a shortest distance between the crown circumferential groove and the main belt located radially inward of the crown circumferential groove is 1.2 to 1.6 times the groove bottom width of the crown circumferential groove.

[0022] (15) Any of the heavy-duty pneumatic tires (1) to (14) above preferably has At least three circumferential grooves are formed in the tread, a crown circumferential groove is a circumferential groove located more inwardly than the shoulder circumferential groove in the axial direction, The crown circumferential groove has an outer portion whose axial width narrows toward the radial inside, and a bottom side portion connected to a radially inner end of the outer portion and whose axial width is constant or narrows toward the radial inside, an opening width of the crown circumferential groove is equal to or greater than twice the groove bottom width of the crown circumferential groove, a depth to a radially inner end of the outer portion is 0.4 to 0.6 times the depth of the crown circumferential groove, The angle a of the wall surface of the bottom side portion with respect to the radial direction is equal to or greater than 0° and equal to or less than 5°, An angle b of the wall surface of the outer portion with respect to the radial direction is greater than the angle a and is not more than 40°.

[0023] (16) In the heavy duty pneumatic tire according to any one of (1) to (15) above, an end of the band is preferably located inside an end of the belt in the axial direction.

[0024] (17) In the heavy-duty pneumatic tire according to any one of (1) to (16), preferably, the main belt includes two or three main belt plies, At least one main belt ply is located radially inside the band, At least one main belt ply is positioned radially outward of the band. Effect of the Invention

[0025] According to the present invention, it is possible to provide a heavy-duty pneumatic tire that ensures good uneven wear resistance, suppresses an increase in tire weight, and inhibits the occurrence of TGC in shoulder circumferential grooves. [Brief description of the drawings]

[0026] [Figure 1] FIG. 1 is a cross-sectional view showing a portion of a heavy duty pneumatic tire according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic diagram illustrating the configuration of the reinforcing layer. [Diagram 3] FIG. 3 is an enlarged cross-sectional view of a portion of the tire of FIG. [Figure 4] FIG. 4 is an enlarged cross-sectional view showing a shoulder circumferential groove and its vicinity provided in the tire of FIG. [Diagram 5] FIG. 5 is an enlarged cross-sectional view showing a middle circumferential groove and its vicinity provided in the tire of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] Hereinafter, the present invention will be described in detail based on preferred embodiments with appropriate reference to the drawings.

[0028] In the present invention, a state in which a tire is mounted on a standard rim, the internal pressure of the tire is adjusted to a standard internal pressure, and no load is applied to the tire is referred to as a standard state.

[0029] In the present invention, unless otherwise specified, the dimensions and angles of each part of the tire are measured in a normal state. The dimensions and angles of each part in the meridian section of the tire, which cannot be measured when the tire is mounted on a regular rim, are measured on the cut surface of the tire obtained by cutting the tire along a plane including the axis of rotation. In this measurement, the tire is set so that the distance between the left and right beads is the same as the distance between the beads of the tire mounted on a regular rim. The tire configuration that cannot be confirmed when the tire is mounted on a regular rim is confirmed on the aforementioned cut surface.

[0030] A genuine rim is a rim that is specified in the standard on which the tire is based. The "standard rim" in the JATMA standard, the "Design Rim" in the TRA standard, and the "Measuring Rim" in the ETRTO standard are genuine rims.

[0031] Normal tire pressure means the internal pressure specified in the standard on which the tire is based. The "maximum air pressure" in the JATMA standard, the "maximum value" listed in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "INFLATION PRESSURE" in the ETRTO standard are normal tire pressures.

[0032] Normal load refers to the load specified in the standard on which the tire is based. The "maximum load capacity" in the JATMA standard, the "maximum value" listed in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "LOAD CAPACITY" in the ETRTO standard are normal loads.

[0033] In the present invention, the "nominal aspect ratio" is the "nominal aspect ratio" included in the "tire designation" defined in JIS D4202 "Automobile tires - designations and specifications".

[0034] In the present invention, the tread of a tire is the part of the tire that comes into contact with the road surface. In this tire, the portion of the tread axially outward from the shoulder circumferential groove (including the radially inner portion of the shoulder circumferential groove) is called the shoulder portion, and the portion axially inward from the shoulder circumferential groove is called the crown portion.

[0035] In the present invention, the number of sections of the cords (number of cords) contained in a tire element containing parallel cords per 5 cm width is expressed as the density of the cords contained in this element (unit: ends / 5 cm). Unless otherwise specified, the cord density is obtained in the cross section of the element obtained by cutting the element in a plane perpendicular to the length direction of the cord.

[0036] 1 shows a part of a heavy-duty pneumatic tire 2 (hereinafter also simply referred to as "tire 2") according to one embodiment of the present invention. This tire 2 is mounted on vehicles such as trucks, buses, and coaches. The nominal aspect ratio of this tire 2 is 70% or more. In other words, this tire 2 has a nominal aspect ratio of 70% or more. This tire 2 is a high aspect tire.

[0037] 1 shows a part of a cross section (hereinafter, meridian cross section) of the tire 2 taken along a plane including the rotation axis of the tire 2. In FIG. 1, the left-right direction is the axial direction of the tire 2, and the up-down direction is the radial direction of the tire 2. The direction perpendicular to the plane of FIG. 1 is the circumferential direction of the tire 2. The dashed-dotted line CL represents the equatorial plane of the tire 2.

[0038] The tire 2 is mounted on a rim (not shown). The rim is a regular rim. Air is filled inside the tire 2, and the internal pressure of the tire 2 is adjusted. The tire 2 mounted on the rim is also called a tire-rim assembly. The tire-rim assembly includes a rim and the tire 2 mounted on the rim.

[0039] The tire 2 includes a tread 4 , a pair of sidewalls 6 , a pair of beads 8 , a pair of chafers 10 , a carcass 12 , an inner liner 16 , a pair of steel fillers 18 , and a reinforcing layer 20 .

[0040] The tread 4 comes into contact with the road surface at its outer surface. This outer surface is a tread surface 22. In Fig. 1, the symbol PC denotes an intersection point between the tread surface 22 and the equatorial plane. This intersection point PC is the equator of the tire 2. The equator PC is the outer end of the tire 2 in the radial direction.

[0041] 1, the symbol PE indicates an end of the tread surface 22. The double arrow WT indicates the width of the tread surface 22. The width WT of the tread surface 22 is represented by the axial distance from an end PE of one tread surface 22 to an end PE of the other tread surface 22.

[0042] Although not shown, the tread 4 can include a base portion and a cap portion located radially outward of the base portion. In this case, both the base and cap are made of crosslinked rubber. The base is made of crosslinked rubber with low heat generation. The cap is made of crosslinked rubber that takes into consideration wear resistance, low temperature characteristics, and grip performance.

[0043] In this tire 2, at least two circumferential grooves 28 are formed in the tread 4. Four circumferential grooves 28 are formed in the tread 4 of the tire 2 shown in Fig. 1. These circumferential grooves 28 are arranged in parallel in the axial direction and extend continuously in the circumferential direction.

[0044] Of the four circumferential grooves 28 engraved in the tread 4, the circumferential groove 28 located on the outer side in the axial direction is the shoulder circumferential groove 28s. The circumferential groove 28 located on the inner side of the shoulder circumferential groove 28s in the axial direction is the middle circumferential groove (crown circumferential groove) 28m. In the tire 2, the four circumferential grooves 28 are composed of a pair of middle circumferential grooves 28m and a pair of shoulder circumferential grooves 28s. In the tire according to the embodiment of the present invention, a circumferential groove located axially inside the two shoulder circumferential grooves and sandwiched between the two shoulder circumferential grooves is called a crown circumferential groove. Also, among the crown circumferential grooves, a circumferential groove adjacent to the shoulder circumferential groove in the axial direction is particularly called a middle circumferential groove.

[0045] It is preferable that the tire 2 is provided with not only shoulder circumferential grooves 28s but also crown circumferential grooves (middle circumferential grooves) 28m. By providing the crown circumferential groove in addition to the shoulder circumferential groove, the movement in the width direction occurring in the circumferential groove is dispersed when the tire 2 repeatedly comes into contact with and out of contact with the ground. Therefore, the strain occurring in the circumferential groove is dispersed, and the risk of TGC occurrence in each circumferential groove including the shoulder circumferential groove is reduced.

[0046] As described above, at least two circumferential grooves 28 are formed in the tread 4 of the tire 2. As a result, at least three land portions 30 are formed in the tread 4. Four circumferential grooves 28 are formed in the tread 4 of the tire 2 shown in Fig. 1, thereby forming five land portions 30. These land portions 30 are arranged in parallel in the axial direction and extend continuously in the circumferential direction.

[0047] Of the five land portions 30 formed in the tread 4, the land portion 30 including the equator PC of the tire is the center land portion 30c. The land portion 30 located on the outer side in the axial direction is the shoulder land portion 30s. The shoulder land portion 30s is located on the outer side of the shoulder circumferential groove 28s in the axial direction and includes the edge PE of the tread surface 22. The land portion 30 located between the center land portion 30c and the shoulder land portion 30s in the axial direction is the middle land portion 30m. Between the middle land portion 30m and the shoulder land portion 30s is the shoulder circumferential groove 28s. Between the middle land portion 30m and the center land portion 30c is the middle circumferential groove 28m. In the tire 2 shown in FIG. 1, the five land portions 30 are composed of the center land portion 30c, a pair of middle land portions 30m, and a pair of shoulder land portions 30s.

[0048] The tire 2 according to the embodiment of the present invention has at least three land portions in the tread. In the embodiment of the present invention, among the at least three land portions, the land portion located on the outer side of the shoulder circumferential groove 28s in the axial direction is the shoulder land portion. In addition, in the embodiment of the present invention, the land portion located on the inner side of the shoulder circumferential groove 28s in the axial direction is the crown land portion. Among the crown land portions, the land portion closest to the equator of the tire in the axial direction is particularly referred to as the center land portion, and the crown land portions other than the center land portion are particularly referred to as the middle land portion.

[0049] In this tire 2, the axial width of the center land portion 30c is 10% or more and 18% or less of the WT of the tread surface 22. The axial width of the middle land portion 30m is 10% or more and 18% or less of the width WT of the tread surface 22. The axial width WF of the shoulder land portion 30s is 15% or more and 25% or less of the width WT of the tread surface 22. The axial width of the land portion 30 is represented by the axial width of the top surface of the land portion 30 that forms part of the tread surface 22.

[0050] In the tire 2 shown in FIG. 1, the land portion 30 formed in the tread 4 is a land portion including the equator PC of the tire, that is, a center land portion 30c. In the tire 2 according to an embodiment of the present invention, the tread 4 may be configured to include a circumferential groove 28 cut into the tread 4 that is centrally located in the axial direction, and the circumferential groove 28 is located on the equatorial plane.

[0051] Each sidewall 6 is continuous with an end of the tread 4. The sidewalls 6 extend radially inward from the end of the tread 4. The sidewalls 6 are made of crosslinked rubber.

[0052] Each bead 8 is located radially inward from the sidewall 6. Each bead 8 includes a core 32 and an apex .

[0053] The core 32 extends in the circumferential direction. The core 32 includes wound steel wire. The core 32 has a generally hexagonal cross-sectional shape.

[0054] The apex 34 is located radially outward of the core 32. The apex 34 includes an inner apex 34u and an outer apex 34s. The inner apex 34u extends radially outward from the core 32. The outer apex 34s is located radially outward of the inner apex 34u. The inner apex 34u is made of a hard crosslinked rubber. The outer apex 34s is made of a crosslinked rubber that is softer than the inner apex 34u. The outer apex 34s is softer than the inner apex 34u.

[0055] Each chafer 10 is located axially outward of the bead 8. The chafers 10 are located radially inward of the sidewall 6. The chafers 10 contact a rim (not shown). The chafers 10 are made of crosslinked rubber in consideration of wear resistance.

[0056] The carcass 12 is located inside the tread 4, the sidewall 6, and the chafer 10. The carcass 12 includes at least one carcass ply 36. The carcass 12 of the tire 2 is made up of one carcass ply 36. The carcass ply 36 is folded up around each core 32 from the inside to the outside in the axial direction.

[0057] Although not shown, the carcass ply 36 includes a number of carcass cords arranged in parallel. These carcass cords are covered with a topping rubber. Each carcass cord intersects with the equatorial plane. In the tire 2, the angle that the carcass cord makes with the equatorial plane (the angle that the carcass cord makes with the circumferential direction) is equal to or greater than 70° and equal to or less than 90°. The carcass 12 has a radial structure. In the tire 2, steel cords are used as the carcass cords.

[0058] The inner liner 16 is positioned inside the carcass 12. The inner liner 16 constitutes the inner surface of the tire 2. The inner liner 16 is made of crosslinked rubber with excellent air barrier properties. The inner liner 16 maintains the internal pressure of the tire 2.

[0059] Each steel filler 18 is located in a portion of a bead 8. The steel filler 18 is folded back around the core 32 from the inside toward the outside in the axial direction along the carcass ply 36.

[0060] Although not shown, the steel filler 18 includes a number of filler cords arranged in parallel. The filler cords are covered with a topping rubber in the steel filler 18. In the tire 2, a steel cord is used as the filler cord.

[0061] The reinforcing layer 20 is located radially inside the tread 4. The reinforcing layer 20 is located between the carcass 12 and the tread 4. The reinforcing layer 20 includes a belt 38 and a band 60.

[0062] Fig. 2 shows the configuration of the reinforcing layer 20. In Fig. 2, the left-right direction is the axial direction of the tire 2, and the up-down direction is the circumferential direction of the tire 2. The direction perpendicular to the paper surface is the radial direction of the tire 2. The front side of the paper surface is the radial outer side, and the back side is the radial inner side.

[0063] In the tire 2, the belt 38 includes a main belt 40 and a pair of sub-belts 48. In the tire 2, the main belt 40 includes one to three main belt plies 42 arranged in the radial direction. Each main belt ply 42 is arranged such that both ends face each other across the equatorial plane. The belt 38 of the tire 2 shown in FIG. 1 includes three main belt plies 42. The three main belt plies 42 include a first main belt ply 42A located on the inside in the radial direction, a second main belt ply 42B located on the outside of the first main belt ply 42A, and a third main belt ply 42C located on the outside of the second main belt ply 42B.

[0064] In the tire 2, the second main belt ply 42B has the widest axial width. The first main belt ply 42A and the third main belt ply 42C have the same axial width, or the axial width of the first main belt ply 42A is wider than the axial width of the third main belt ply 42C. The axial width of each main belt ply 42 is represented by the axial distance from one end 42e of the main belt ply 42 to the other end 42e.

[0065] The end 38e of the belt 38 of the tire 2 is represented by the end of the main belt ply 42 having the widest axial width among the multiple main belt plies 42 constituting the main belt 40. As described above, in the tire 2, the second main belt ply 42B has the widest axial width among the three main belt plies 42 constituting the main belt 40. The end 38e of the belt 38 of the tire 2 is represented by the end 42Be of the second main belt ply 42B having the widest axial width. The end 38e of the belt 38 is also the end 20e of the reinforcing layer 20.

[0066] 1, an end 42Ae of the first main belt ply 42A is located outside the shoulder circumferential groove 28s in the axial direction. An end 42Be of the second main belt ply 42B is located outside the shoulder circumferential groove 28s in the axial direction. An end 42Ce of the third main belt ply 42C is located outside the shoulder circumferential groove 28s in the axial direction.

[0067] In the tire 2, from the viewpoint of ensuring rigidity of the tread 4 portion, the ratio of the axial width of the first main belt ply 42A to the width WT of the tread surface 22 is preferably equal to or greater than 0.80 and is preferably equal to or less than 0.90. A ratio of the axial width W2 of the second main belt ply 42B to the width WT of the tread surface 22 is preferably equal to or greater than 0.85 and is preferably equal to or less than 0.95. A ratio of the axial width W3 of the third main belt ply 42C to the width WT of the tread surface 22 is preferably equal to or greater than 0.80 and is preferably equal to or less than 0.90.

[0068] The pair of sub-belts 48 are arranged to be spaced apart from each other in the axial direction across the equatorial plane, as shown in Fig. 1. Each of the sub-belts 48 is made up of one belt ply (also referred to as a sub-belt ply 50). In this tire 2, each sub-belt 48 is located between the tread 4 and the main belt 40. The sub-belt 48 is located so as to overlap with the shoulder circumferential groove 28s in the radial direction. At this time, both ends (inner end 48ue, outer end 48se) of the sub-belt 48 are located so as not to overlap with the shoulder circumferential groove 28s in the radial direction. In other words, the outer end 48se of the sub-belt 48 is located axially outward from the outer edge Se2 of the shoulder circumferential groove 28s, and the inner end 48ue of the sub-belt 48 is located axially inward from the inner edge Se1 of the shoulder circumferential groove 28s. In the tire 2, the shoulder circumferential groove 28s entirely overlaps with the sub-belt 48 in the radial direction.

[0069] As shown in FIG. 1, the sub-belt 48 is provided so as to be in contact with the main belt ply that is located radially outermost among the plurality of main belt plies 42, that is, the third main belt ply 42C. Furthermore, the outer end 48se of the sub-belt 48 is located inside the end 42Ce of the third main belt ply 42C in the axial direction. When the outer end 48se of the sub-belt 48 and the end 42Ce of the third main belt ply 42C are close to each other, the ends of the belts with large distortion are close to each other, so there is a concern that BEL (belt edge loose) may occur. BEL is damage in which a belt cord peels off from the surrounding rubber at the end of a layer constituting the belt (the end of the belt). The occurrence of BEL leads to a deterioration in durability.

[0070] In FIG. 1, a double-headed arrow WA indicates the axial distance between an outer end 48se of the sub-belt 48 and an end 42Ce of a third main belt ply 42C that is located radially outermost among the multiple main belt plies 42. In the tire 2, it is preferable that the outer end 48se of the sub-belt 48 is provided axially inward of the end 42Ce of the third main belt ply 42C so that the distance WA is 5 mm or more. In this case, BEL is further prevented from occurring, which leads to improved durability.

[0071] 2, in the tire 2, each main belt ply 42 constituting the belt 38 includes a large number of belt cords 44 arranged in parallel. In addition, the sub-belt ply 50 constituting the belt 38 also includes a large number of belt cords 44 arranged in parallel. 2, for convenience of explanation, the belt cord 44 is represented by a solid line, but the belt cord 44 is covered with a topping rubber 46. The belt cord 44 of this tire 2 is a steel cord.

[0072] In the tire 2, the density of the belt cords 44 in each main belt ply 42 is 15 ends / 5 cm or more and 30 ends / 5 cm or less. The density of the belt cords 44 is represented by the number of cross sections of the belt cords 44 included per 5 cm width of the main belt ply 42 in a cross section of the main belt ply 42 along a plane perpendicular to the extension direction of the belt cords 44. The density of the belt cords 44 in each main belt ply 42 may be the same or different.

[0073] In the tire 2, the density of the belt cords 44 in the sub-belt ply 50 is 15 ends / 5 cm or more and 30 ends / 5 cm or less. The density of the belt cords 44 is represented by the number of cross sections of the belt cords 44 included per 5 cm width of the sub-belt ply 50 in a cross section of the sub-belt ply 50 along a plane perpendicular to the extension direction of the belt cords 44. The density of the belt cords 44 in the sub-belt ply 50 may be the same as or different from the density of the belt cords 44 in the main belt ply 42 .

[0074] In each main belt ply 42, the belt cord 44 is inclined with respect to the equatorial plane (with respect to the circumferential direction). The direction of inclination of the belt cord 44 included in the first main belt ply 42A with respect to the circumferential direction (hereinafter, the inclination direction of the first main belt ply 42A) is the same as the direction of inclination of the belt cord 44 included in the second main belt ply 42B with respect to the circumferential direction (hereinafter, the inclination direction of the second main belt ply 42B). The inclination direction of the second main belt ply 42B is opposite to the direction of inclination of the belt cord 44 included in the third main belt ply 42C with respect to the circumferential direction (hereinafter, the inclination direction of the third main belt ply 42C). The inclination direction of the first main belt ply 42A may be opposite to the inclination direction of the second main belt ply 42B. The inclination direction of the second main belt ply 42B may be the same as the inclination direction of the third main belt ply 42C, but from the viewpoint of ensuring a stable ground contact shape, it is preferable that the inclination direction of the second main belt ply 42B is opposite to the inclination direction of the third main belt ply 42C.

[0075] In Fig. 2, angle θ1 is an inclination angle of the belt cord 44 included in the first main belt ply 42A with respect to the equatorial plane (hereinafter, first inclination angle θ1). Angle θ2 is an inclination angle of the belt cord 44 included in the second main belt ply 42B with respect to the equatorial plane (hereinafter, second inclination angle θ2). Angle θ3 is an inclination angle of the belt cord 44 included in the third main belt ply 42C with respect to the equatorial plane (hereinafter, third inclination angle θ3).

[0076] In the tire 2, the first inclination angle θ1, the second inclination angle θ2, and the third inclination angle θ3 are preferably 10° or more and 60° or less. From the viewpoint of effectively restraining the movement of the tire 2 and ensuring a stable ground contact shape, the first inclination angle θ1 is preferably 40° or more and 60° or less. The second inclination angle θ2 is preferably 10° or more and 20° or less. The third inclination angle θ3 is preferably 10° or more and 20° or less.

[0077] In the sub-belt 48, the belt cords 44 are inclined with respect to the equatorial plane (with respect to the circumferential direction). The direction of inclination of the belt cords 44 included in the sub-belt ply 50 with respect to the circumferential direction (hereinafter, the inclination direction of the sub-belt 48) is opposite to the inclination direction of the third main belt ply 42C. Note that the inclination direction of the sub-belt ply 50 may be the same as the inclination direction of the third main belt ply 42C. The inclination direction of the sub-belt 48 and the inclination direction of the third main belt ply 42C are preferably opposite to each other.

[0078] In FIG. 2, the inclination direction of one sub-belt 48A and the inclination direction of the other sub-belt 48B of the pair of sub-belts 48 are the same, but the inclination direction of one sub-belt 48A and the inclination direction of the other sub-belt 48B may be opposite. The inclination direction of one sub-belt 48A and the inclination direction of the other sub-belt 48B are preferably the same.

[0079] In Fig. 2, angle θ4 is an inclination angle (hereinafter, referred to as a fourth inclination angle θ4) of the belt cord 44 included in the sub-belt ply 50 with respect to the equatorial plane. This angle θ4 is an angle at which the belt cord 44 included in the sub-belt 48 is inclined with respect to the equatorial plane (with respect to the circumferential direction). This fourth inclination angle θ4 is 20° or more. The fourth inclination angle θ4 is preferably equal to or greater than 30° and equal to or less than 80°. In this case, it is suitable to suppress the dimensional growth of the shoulder portion of the tread 4 while suppressing the bending of the shoulder circumferential groove 28s in the axial direction.

[0080] If the fourth inclination angle θ4 is less than 30°, the dimensional growth in the shoulder portion of the tread 4 can be suppressed, but the performance of suppressing the axial bending of the shoulder circumferential groove 28s is inferior, so that when the tire 2 is repeatedly in and out of contact with the ground, the occurrence of TGC in the shoulder circumferential groove 28s may not be sufficiently suppressed. On the other hand, when the fourth inclination angle θ4 exceeds 80°, the dimensional growth in the shoulder portion cannot be sufficiently suppressed, and as a result, the occurrence of TGC due to the opening of the shoulder circumferential groove 28s may not be sufficiently suppressed. In addition, the tire 2 is a high aspect tire, and the tread pressure distribution rate is smaller than that of a low aspect tire, so the growth of the shoulder portion is small. Therefore, the sub-belt 48 can be configured to be more suitable for ensuring rigidity in the width direction than for dimensional growth, and the fourth inclination angle θ4 can be set to a relatively large angle.

[0081] From the viewpoint of suppressing the dimensional growth of the shoulder portion of the tread 4 of the tire 2, particularly the radial dimensional growth of the shoulder portion, the fourth inclination angle θ4 is more preferably equal to or greater than 30° and equal to or less than 50°.

[0082] From the viewpoint of suppressing bending in the axial direction in the shoulder circumferential groove 28s of the tire 2, the fourth inclination angle θ4 is more preferably equal to or greater than 50° and equal to or less than 80°.

[0083] The tire 2 includes a band 60 as the reinforcing layer 20 . 1, the band 60 has opposite ends 60e across an equatorial plane, and extends axially from the equatorial plane toward each end 60e. The end 60e of the band 60 is located outside the shoulder circumferential groove 28s in the axial direction, and the band 60 is located inside the shoulder circumferential groove 28s in the radial direction. In the tire 2, the band 60 is located on the outer side of the second main belt ply 42B and on the inner side of the third main belt ply 42C in the radial direction.

[0084] In this tire 2, deformation near the shoulder circumferential groove 28s is effectively suppressed by the band 60. Changes in the shape of the tire 2, for example, the outline of the carcass 12 (hereinafter also referred to as the case line), are suppressed, so that changes in the ground contact shape are suppressed. In addition, because changes in the ground contact shape are suppressed, the occurrence of TGC in the circumferential grooves and uneven wear in the shoulder portion are also suppressed.

[0085] 2, the band 60 includes a spirally wound band cord 62. In FIG. 2, the band cord 62 is shown by a solid line for convenience of explanation, but the band cord 62 is covered with a topping rubber 64.

[0086] In the tire 2, the band cord 62 is a steel cord. The band cord 62 may be a cord made of organic fiber (hereinafter, organic fiber cord). When an organic fiber cord is used as the band cord 62, examples of the organic fiber include nylon fiber, polyester fiber, rayon fiber, and aramid fiber.

[0087] The band 60 includes a spirally wound band cord 62. The band 60 has a jointless structure. In the band 60, the angle that the band cord 62 makes with the circumferential direction is preferably 5° or less, and more preferably 2° or less. The band cord 62 of the band 60 extends substantially in the circumferential direction.

[0088] The density of the band cord 62 in the band 60 is 20 ends / 5 cm or more and 35 ends / 5 cm or less. The density of the band cord 62 is represented by the number of cross sections of the band cord 62 contained per 5 cm width of the band 60 in a cross section of the band 60 along a plane perpendicular to the extension direction of the band cord 62.

[0089] Fig. 3 shows a part of the cross section of the tire 2 shown in Fig. 1. In Fig. 3, the left-right direction is the axial direction of the tire 2, and the up-down direction is the radial direction of the tire 2. The direction perpendicular to the paper surface of Fig. 3 is the circumferential direction of the tire 2.

[0090] In this tire 2, the end 42Be of the second main belt ply 42B and the end 42Ce of the third main belt ply 42C are covered with a rubber layer 56. Two more rubber layers 56 are disposed between the end 42Be of the second main belt ply 42B and the end 42Ce of the third main belt ply 42C, which are covered with the rubber layer 56. In this tire 2, an edge member 58 consisting of a total of four rubber layers 56 is configured between the end 42Be of the second main belt ply 42B and the end 42Ce of the third main belt ply 42C. The edge member 58 is made of crosslinked rubber. The edge member 58 contributes to maintaining the interval between the end 42Be of the second main belt ply 42B and the end 42Ce of the third main belt ply 42C. In this tire 2, the change in the positional relationship between the end 42Be of the second main belt ply 42B and the end 42Ce of the third main belt ply 42C due to running is suppressed. The edge member 58 is a part of the reinforcing layer 20. The reinforcing layer 20 of the tire 2 includes a pair of edge members 58 in addition to the belt 38 and the band 60 .

[0091] 3, the double-headed arrow WB indicates the axial distance between the outer end 48se of the sub-belt 48 and the outer edge Se2 of the shoulder circumferential groove 28s. The double-headed arrow WC indicates the axial distance between the inner end 48ue of the sub-belt 48 and the inner edge Se1 of the shoulder circumferential groove 28s. In the tire 2, each of the axial distance WB and the axial distance WC is preferably 50% or more of the opening width WSS (see FIG. 4) of the shoulder circumferential groove. In this case, the sub-belt 48 has a width dimension suitable for suppressing bending of the shoulder circumferential groove and preventing the occurrence of TGC.

[0092] In Figure 3, MMP is the axial midpoint of the top surface of the middle land section 30 m. In the tire 2, the inner end 48ue of the sub-belt 48 is located axially outside the axial midpoint MMP of the middle land portion 30m. Even if the inner end 48ue of the sub-belt 48 extends to the inside of the axial midpoint MMP, the improvement in the effect of suppressing the bending of the shoulder circumferential groove is small, and excess material is used, which leads to an increase in the weight of the tire 2. In addition, when the inner end 48ue of the sub-belt 48 approaches the middle circumferential groove 30m, the rigidity difference between the radially lower portion of the middle circumferential groove 30m and other portions becomes large, and there is a risk that TGC is more likely to occur in the middle circumferential groove 30m.

[0093] In Fig. 3, the double-headed arrow WD indicates the axial distance from the shoulder circumferential groove 28s, more specifically, from the groove bottom center of the shoulder circumferential groove 28s to the equator PC of the tire 2. Here, the groove bottom center of the shoulder circumferential groove 28s refers to a bottom portion of the shoulder circumferential groove 28s that contacts an imaginary line VL1 shown in Fig. 4, which will be described later. In this case, if this portion is a line segment, the axial midpoint of this line segment is referred to as the groove bottom center. The axial distance WD is preferably 45% or more and 75% or less of the half width WHT of the tread surface 2 . When the ratio ([WD / WHT]×100) of the axial distance WD to half the width WHT of the tread surface 2 is less than 45%, the degree of axial bending in the shoulder circumferential groove 28s is small to begin with, so even if the sub-belt 48 is provided, the effect of suppressing the occurrence of TGC in the shoulder circumferential groove 28s is small. On the other hand, when the ratio ([WD / WHT]×100) exceeds 75%, it becomes difficult to ensure the axial distance WA between the end 42Ce of the third main belt ply 42C and the outer end 48se of the sub-belt 48. Therefore, there is a concern that the durability may deteriorate due to the occurrence of BEL.

[0094] FIG. 4 is an enlarged cross-sectional view showing a shoulder circumferential groove 28s provided in the tire 2 of FIG. 1 and its vicinity. 4, which shows a meridian cross section of the shoulder circumferential groove 28s, the double arrow WSS indicates the opening width of the shoulder circumferential groove 28s, the double arrow WSU indicates the groove bottom width of the shoulder circumferential groove 28s, and the double arrow DS indicates the depth of the shoulder circumferential groove 28s.

[0095] As shown in Fig. 4, the shoulder circumferential groove 28s of the tire 2 has a generally U-shaped cross-sectional shape that gradually narrows toward the radially inner side. In this cross-sectional shape, the wall surface of the shoulder circumferential groove 28s is composed of two line segments 128s1 and 128s2 and two circular arcs 128s3 and 128s4 of radius Rb that convex toward the radially inner side and connect the radially inner ends of the line segments. The radially inner ends of the two straight lines 128s1 and 128s2 may be connected by a single circular arc.

[0096] The opening width WSS of the shoulder circumferential groove 28s is represented by the shortest distance between an inner edge Se1 of the shoulder circumferential groove 28s and an outer edge Se2 of the shoulder circumferential groove 28s. The groove bottom width WSU of the shoulder circumferential groove 28s is expressed as the distance between points VP1 and VP2, where VP1 is the intersection point between an imaginary line VL1 that contacts the bottom of the shoulder circumferential groove 28s and extends in the axial direction and an extension of a line segment 128s1 that constitutes part of the shoulder circumferential groove 28s, and VP2 is the intersection point between the imaginary line VL1 and an extension of a line segment 128s2. The depth DS of the shoulder circumferential groove 28s is represented by the distance from the tread surface 22 to the bottom of the shoulder circumferential groove 28s.

[0097] In the shoulder circumferential groove 28s having the cross-sectional shape shown in FIG. 4, the radius Rb of each of the circular arcs 128s3, 128s4 is preferably 2.5 mm or more. In this case, strain is dispersed in the groove bottom portion of the shoulder circumferential groove 28s, making it more difficult for TGC to occur in the shoulder circumferential groove 28s.

[0098] From the viewpoint of contributing to drainage and traction performance, the opening width WSS of the shoulder circumferential groove 28s having the cross-sectional shape shown in Fig. 4 is preferably about 1 to 7% of the width WT of the tread surface 22. The depth DS of the shoulder circumferential groove 28s is preferably, for example, 13 to 25 mm.

[0099] In the shoulder circumferential groove 28s having the cross-sectional shape shown in FIG. 4, the groove bottom width WSU of the shoulder circumferential groove 28s is, for example, not less than 4 mm and not more than 13 mm.

[0100] 3, the double-headed arrow GB indicates the shortest distance between the shoulder circumferential groove 28s and the sub-belt 48 located radially inside the shoulder circumferential groove 28s. This distance GB is preferably 0.5 to 1.5 times the groove bottom width WSU of the shoulder circumferential groove 28s. The shorter the distance GB, in other words, the thinner the thickness of the rubber located radially inside the shoulder circumferential groove 28s, the lighter the tire 2 becomes, which is advantageous in terms of RRC. On the other hand, if the distance GB is short, when a foreign object such as a stone gets caught in the shoulder circumferential groove 28s, the sub-belt 48 is more likely to be damaged by drilling (a phenomenon in which a foreign object penetrates into the tread 4 from the groove bottom of the circumferential groove and damages the internal structure of the tire 2) caused by the caught foreign object. In addition, if the distance GB is short, the total amount of antioxidant contained in the crosslinked rubber radially inside the shoulder circumferential groove 28s decreases, so that the rubber is more likely to age and TGC is more likely to occur.

[0101] FIG. 5 is an enlarged cross-sectional view showing the middle circumferential groove 28m provided in the tire 2 of FIG. 1 and its vicinity. The middle circumferential groove 28m has an outer portion 28ms whose axial width narrows toward the radially inward direction, and a bottom portion 28mu that is connected to the radially inner end of the outer portion and whose axial width is constant or narrows toward the radially inward direction.

[0102] In Fig. 5, which shows a meridian cross section of the middle circumferential groove 28m, the double arrow WMS is the opening width of the middle circumferential groove 28m. The double arrow WMU is the groove bottom width WMU of the middle circumferential groove 28m. The double arrow DM is the depth of the middle circumferential groove 28m. The double arrow DMS is the depth of the outer portion 28ms of the middle circumferential groove 28m. The double arrow DMU is the depth of the bottom side portion 28mu of the middle circumferential groove 28m.

[0103] As shown in Fig. 5, the middle circumferential groove 28m of the tire 2 has an outer portion 28ms whose width gradually narrows toward the radial inside, and a bottom portion 28mu whose axial width is constant or narrows toward the radial inside and is connected to the radial inside ends Me3 and Me4 of the outer portion 28ms, and has a substantially Y-shaped cross section. In this cross section, the wall surface of the groove 28m is composed of two line segments 128m1 and 128m2 whose distance gradually approaches the radial inside, two parallel line segments 128m3 and 128m4 connected to the radial inside ends Me3 and Me4 of the line segments 128m1 and 128m2, and a curved line 128m5 that convexly faces the radial inside and connects the radial inside ends of the line segments 128m3 and 128m4. The radial inside ends of the line segments 128m3 and 128m4 may be connected to each other by a circular arc.

[0104] The opening width WMS of the middle circumferential groove 28m is represented by the shortest distance between an inner edge Me1 of the middle circumferential groove 28m and an outer edge Me2 of the middle circumferential groove 28m. The groove bottom width WMU of the middle circumferential groove 28m is expressed as the distance between point VP3 and point VP4, where VP3 is the intersection point between an imaginary line VL2 that contacts the bottom of the middle circumferential groove 28m and extends in the axial direction and an extension of a line segment 128m3 that constitutes part of the middle circumferential groove 28m, and VP2 is the intersection point between the imaginary line VL2 and an extension of a line segment 128m4. The depth DM of the middle circumferential groove 28m is expressed as the distance from the tread surface 22 to the bottom of the middle circumferential groove 28m. The depth DMS of the outer portion 28ms of the middle circumferential groove 28m is represented by the shortest distance between the tread surface 22 and a line segment connecting radially inner ends Me3, Me4 of the line segments 128m1, 128m2. The depth DMU of the bottom side portion 28mu of the middle circumferential groove 28m is expressed as the difference between the depth DM of the middle circumferential groove 28m and the depth DMS of the outer portion 28ms of the middle circumferential groove 28m.

[0105] In the middle circumferential groove 28m having the cross-sectional shape shown in Fig. 5, the groove bottom width WMU of the middle circumferential groove 28m is preferably 0.5 times or less the opening width WMS of the middle circumferential groove 28m. If the groove bottom width WMU of the middle circumferential groove 28m is wide, the middle circumferential groove 28m is likely to be trapped with stones, and the main belt 42 is likely to be damaged by drilling of the trapped stones. The groove bottom width WMU of the middle circumferential groove 28m is preferably 0.1 times or more the opening width WMS of the middle circumferential groove 28m.

[0106] From the viewpoint of contributing to drainage and traction performance, the opening width WMS of the middle circumferential groove 28m having the cross-sectional shape shown in Fig. 5 is preferably about 2 to 10% of the width WT of the tread surface 22. The depth DM of the middle circumferential groove 28m is preferably 13 to 25 mm.

[0107] The groove bottom width WMU of the middle circumferential groove 28m is preferably 5 mm or less. In this case, the middle circumferential groove 28m is less likely to be trapped by stones. Therefore, drilling due to trapped stones is less likely to occur. The groove bottom width WMU of the middle circumferential groove 28m is more preferably 3 mm or less. A groove bottom width WMU of the middle circumferential groove 28m is preferably equal to or greater than 1 mm, and more preferably equal to or greater than 2 mm.

[0108] 3, the double-headed arrow GA indicates the shortest distance between the middle circumferential groove 28m and the main belt 42 (third main belt ply 42C) located radially inside the middle circumferential groove 28m. When the groove bottom width WMU of the middle circumferential groove 28m is 5 mm or less, the distance GA is preferably 1.2 to 1.6 times the groove bottom width WMU of the middle circumferential groove 28m. In this case, since the groove bottom width WMU is narrow at 5 mm or less, the stones that get caught in the groove bottom width WMU are small, and if the distance GA is within the above range, it is suitable for preventing damage to the main belt 42 without deteriorating the RRC of the tire 2. If the distance GA is less than 1.2 times the groove bottom width WMU, the thickness of the rubber located radially inside the middle circumferential groove 28m is thin, which makes the main belt 42 more likely to be damaged. On the other hand, if the distance GA is more than 1.6 times the groove bottom width WMU, the thickness of the rubber located radially inside the middle circumferential groove 28m is thick, which makes the weight of the tire 2 heavy, which makes the RCC more likely to deteriorate.

[0109] When the middle circumferential groove 28m has the cross-sectional shape shown in Figs. 3 and 5, each dimension of the middle circumferential groove 28m preferably satisfies the following requirements (a) to (d). (a) The opening width WMS of the middle circumferential groove 28m is preferably at least twice the groove bottom width WMU of the middle circumferential groove 28m. If the opening width WMS is less than twice the groove bottom width WMU, the volume of the middle circumferential groove 28m is small, and the WET performance of the tire 2 may become insufficient.

[0110] (b) The depth DMS of the outer portion 28ms of the middle circumferential groove 28m (hereinafter, the depth of the outer portion 28ms) is preferably 0.4 to 0.6 times the depth DM of the middle circumferential groove 28m. If the depth of the outer portion 28ms is less than 0.4 times the depth DM of the middle circumferential groove 28m, the volume of the middle circumferential groove 28m is small, and the WET performance of the tire 2 may become insufficient. On the other hand, if the depth of the outer portion 28ms exceeds 0.6 times the depth DM of the middle circumferential groove 28m, the depth DMU of the bottom portion 28mu of the middle circumferential groove 28m cannot be sufficiently secured, so stones become more likely to penetrate into the bottom portion of the middle circumferential groove 28m, making drilling more likely to occur.

[0111] (c) In the middle circumferential groove 28m, the angle a of the wall surfaces 128m3, 128m4 of the bottom side portion 28mu with respect to the radial direction is preferably equal to or greater than 0° and equal to or less than 5°. If the angle a between the wall surfaces 128m3, 128m4 of the bottom side portion 28mu exceeds 5°, stones will easily get into the bottom side portion 28mu of the middle circumferential groove 28m, making drilling more likely to occur.

[0112] (d) In the middle circumferential groove 28m, the angle b of the wall surfaces 128m1, 128m2 of the outer portion 28ms with respect to the radial direction is preferably greater than the angle a and is equal to or smaller than 40°. If the angle b is greater than 40°, the volume of the middle circumferential groove 28m increases, which is advantageous for the wet performance of the tire 2, but the volume of the land portion in the tread 4 decreases, which may deteriorate the wear resistance of the tread surface 22. In addition, the shape of the land portion of the rib from the front side of the middle circumferential groove 28m to the radial inner ends Me3 and Me4 of the outer portion 28ms changes sharply, which reduces the rigidity of the tread 4 and results in poor uneven wear resistance. It is more preferable that the angle b is 10° or more.

[0113] 3, the double-headed arrow WE indicates the axial distance from the outer edge Se2 of the shoulder circumferential groove 28s to the end 60e of the band 60. The double-headed arrow WF indicates the axial width of the shoulder land portion 30s. This axial width WF is represented by the axial distance from the inner end of the top surface of the shoulder land portion 30s (i.e., the outer edge Se2 of the shoulder circumferential groove 28s) to the outer end of this top surface (in this tire 2, the end PE of the tread surface 22).

[0114] In the tire 2, the ratio ([WE / WF]×100) of the axial distance WE from the shoulder circumferential groove 28s to the end 60e of the band 60 to the axial width WF of the shoulder land portion 30s is preferably 50% or less. As a result, the end 60e of the band 60 is disposed away from the end portion of the tread 4 that actively moves during running, so that tension fluctuations in the band cord 62 are suppressed. In the tire 2, the occurrence of breakage of the band cord 62 is suppressed. The band 60 of the tire 2 contributes to suppressing shape change. From this viewpoint, the ratio ([WE / WF]×100) is more preferably 35% or less, and further preferably 25% or less.

[0115] By setting the ratio ([WE / WF]×100) to 10% or more, the end 60e of the band 60 is disposed at an appropriate distance from the shoulder circumferential groove 28s. In the tire 2, the occurrence of damage originating from the groove bottom portion of the shoulder circumferential groove 28s is suppressed. Since the width of the band 60 is ensured, the band 60 contributes to suppressing deformation of the tire 2. From this viewpoint, the ratio ([WE / WF]×100) is more preferably 15% or more.

[0116] In the tire 2, the end 60e of the band 60 is located inside the end 38e of the belt 38 in the axial direction. The belt 38 is wider than the band 60. The belt 38 restrains the end 60e of the band 60. The belt 38 contributes to suppressing the tension fluctuation of the band cord 62 included in the band 60. Since the occurrence of breakage of the band cord 62 due to tension fluctuation is suppressed, the band 60 can stably exert the function of suppressing shape change. From this viewpoint, it is preferable that the end 60e of the band 60 is located inside the end 38e of the belt 38 in the axial direction.

[0117] A force acts on the band 60 of the tire 2 so as to expand from the inside to the outside in the radial direction. This force generates tension in the band cord 62 of the band 60. In this tire 2, the second main belt ply 42B is located on the inside of the band 60 in the radial direction.

[0118] In the tire 2, the second main belt ply 42B suppresses the force acting on the band 60, so that the tension of the band cord 62 included in the band 60 is appropriately maintained. The second main belt ply 42B contributes to suppressing the tension fluctuation of the band cord 62. Since the second main belt ply 42B is wider than the band 60, the tension fluctuation of the band cord 62 is effectively suppressed. In the tire 2, the band cord 62 of the band 60 is unlikely to break. The band 60 can stably exert the function of suppressing the shape change. From this viewpoint, it is preferable that at least one of the main belt plies 42 is located on the inner side of the band 60 in the radial direction. It is preferable that at least one of the main belt plies 42 located on the inner side of the band 60 has a width wider than the width of the band 60.

[0119] In addition, in the tire 2, from the viewpoint of suppressing tension fluctuations in the band cord 62 of the band 60 and making it less likely that the band cord will break due to tension fluctuations, it is more preferable that in the tire 2, a main belt ply 42 wider than the band 60 is positioned radially inside the band 60, and that a main belt ply 42 wider than the band 60 is also positioned outside the band 60.

[0120] Furthermore, from a similar viewpoint, in the tire 2, it is further preferable that the first main belt ply 42A, the second main belt ply 42B and the third main belt ply 42C have a width wider than the width of the band 60, and that the first main belt ply 42A and the second main belt ply 42B are located inside the band 60 and the third main belt ply 42C is located outside the band 60 in the radial direction. In the tire 2, the band 60 may be sandwiched between the first main belt ply 42A and the second main belt ply 42B.

[0121] As is clear from the above description, the present invention provides a heavy-duty pneumatic tire that ensures good uneven wear resistance and suppresses the occurrence of TGC in the shoulder circumferential grooves while suppressing an increase in tire weight. The present invention exerts a remarkable effect on a high-profile heavy-duty pneumatic tire 2 having a nominal aspect ratio of 70% or more. [Industrial Applicability]

[0122] The above-described technique for suppressing the occurrence of TGC in the shoulder circumferential groove while suppressing an increase in tire weight can be applied to various tires. [Explanation of symbols]

[0123] 2. Tires 4. Tread 20... Reinforcement layer 20e: End of reinforcing layer 20 22 Tread surface 28, 28s, 28m...Circumferential groove 30, 30s, 30m, 30c...Land 38. Belt 40 Main belt 42 Main belt ply 44 Belt cord 48...Sub belt 50···Sub-belt ply 60...Band 60e: End of band 60 62...Band cord

Claims

1. The nominal aspect ratio is 70% or more, The tire has a tread that comes into contact with a road surface, and a reinforcing layer that is located radially inside the tread, At least two circumferential grooves are formed in the tread to form at least three land portions arranged in parallel in the axial direction, and the circumferential groove located on the outer side in the axial direction among the at least two circumferential grooves is a shoulder circumferential groove, and the land portion located on the outer side of the shoulder circumferential groove in the axial direction is a shoulder land portion, The reinforcing layer includes a belt including a number of parallel belt cords, and a band including a spirally wound band cord and having both ends opposed to each other across an equator plane, The belt includes a main belt having opposite ends facing each other across an equatorial plane, and a pair of sub-belts spaced apart from each other in the axial direction so as to sandwich the equatorial plane, The main belt includes one to three main belt plies arranged in a radial direction, The sub-belt is provided at a position overlapping the shoulder circumferential groove in the radial direction, while both ends of the sub-belt do not overlap the shoulder circumferential groove, The belt cord included in the sub-belt is inclined at an angle of 20° or more with respect to the circumferential direction. Heavy duty pneumatic tires.

2. The heavy-duty pneumatic tire according to claim 1 , wherein an angle formed by the belt cords included in the sub-belt with respect to the circumferential direction is equal to or greater than 30° and equal to or less than 80°.

3. The heavy-duty pneumatic tire according to claim 2 , wherein an angle formed by the belt cords included in the sub-belt with respect to the circumferential direction is equal to or greater than 30° and equal to or less than 50°.

4. The heavy-duty pneumatic tire according to claim 2 , wherein an angle formed by the belt cords included in the sub-belt with respect to the circumferential direction is equal to or greater than 50° and equal to or less than 80°.

5. The heavy-duty pneumatic tire according to claim 1 or 2, wherein an outer end of the sub-belt is axially positioned more inward than an end of the main belt ply that is radially outermost.

6. 3. The heavy-duty pneumatic tire according to claim 1, wherein an outer end of the sub-belt is located 5 mm or more inward from an end of the main belt ply located outermost in the radial direction.

7. At least three circumferential grooves are formed in the tread, a crown circumferential groove is a circumferential groove located more inwardly than the shoulder circumferential groove in the axial direction, a land portion sandwiched between the shoulder circumferential groove and the crown circumferential groove in the axial direction is a middle land portion, The axial distance between the outer end of the sub-belt and the outer edge of the shoulder circumferential groove, and the axial distance between the inner end of the sub-belt and the inner edge of the shoulder circumferential groove are each 50% or more of the opening width of the shoulder circumferential groove, The heavy duty pneumatic tire according to claim 1 or 2, wherein an inner end of the sub-belt is positioned axially outward of a midpoint of the middle land portion in the axial direction.

8. 3. The heavy-duty pneumatic tire according to claim 1, wherein an axial distance between the shoulder circumferential groove and an equatorial plane is 45% or more and 75% or less of half the axial width of the tread.

9. a groove bottom shape of the shoulder circumferential groove in a meridian cross section is a shape formed by a circular arc, The heavy duty pneumatic tire according to claim 1 or 2, wherein the radius of the arc is 2.5 mm or more.

10. 3. The heavy-duty pneumatic tire according to claim 1, wherein a shortest distance between the shoulder circumferential groove and the sub-belt located radially inside the shoulder circumferential groove is 0.5 to 1.5 times a groove bottom width of the shoulder circumferential groove.

11. At least three circumferential grooves are formed in the tread, a crown circumferential groove is a circumferential groove located more inwardly than the shoulder circumferential groove in the axial direction, The heavy load pneumatic tire according to claim 1 or 2, wherein a groove bottom width of the crown circumferential groove is 0.5 times or less an opening width of the crown circumferential groove.

12. The heavy load pneumatic tire according to claim 11, wherein a groove bottom width of the crown circumferential groove is equal to or greater than 1 mm and equal to or less than 5 mm.

13. The heavy load pneumatic tire according to claim 11, wherein a groove bottom width of the crown circumferential groove is equal to or greater than 2 mm and equal to or less than 3 mm.

14. 12. The heavy load pneumatic tire according to claim 11, wherein a shortest distance between the crown circumferential groove and the main belt located radially inward of the crown circumferential groove is 1.2 times or more and 1.6 times or less a groove bottom width of the crown circumferential groove.

15. At least three circumferential grooves are formed in the tread, a crown circumferential groove is a circumferential groove located more inwardly than the shoulder circumferential groove in the axial direction, The crown circumferential groove has an outer portion whose axial width narrows toward the radial inside, and a bottom side portion connected to a radially inner end of the outer portion and whose axial width is constant or narrows toward the radial inside, an opening width of the crown circumferential groove is equal to or greater than twice the groove bottom width of the crown circumferential groove, a depth to a radially inner end of the outer portion is 0.4 to 0.6 times the depth of the crown circumferential groove, The angle a of the wall surface of the bottom side portion with respect to the radial direction is equal to or greater than 0° and equal to or less than 5°, The heavy-duty pneumatic tire according to claim 1 or 2, wherein an angle b of the wall surface of the outer portion with respect to the radial direction is larger than the angle a and is not larger than 40°.

16. 3. The heavy-duty pneumatic tire according to claim 1, wherein an end of the band is located inside an end of the belt in the axial direction.

17. The main belt includes two or three main belt plies, At least one main belt ply is located radially inside the band, The heavy-duty pneumatic tire according to claim 1 or 2, wherein at least one main belt ply is positioned radially outward of the band.

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