Tire for heavy load

Abstract

To provide a tire 2 for heavy load which can achieve enhancement of uneven wear property and durability.SOLUTION: A tire 2 is provided with a reinforcement layer 24 which is situated between a carcass 12 and a tread 4. The reinforcement layer 24 comprises a belt 66 and a band 68. A belt 66 comprises an inside belt ply 92 and an outside belt ply 94. A direction of inclination of a belt cord which is contained in the inside belt ply 92 is reverse to a direction of inclination of the belt cord which is contained in the outside belt ply 94. A band 68 is provided with a full band 80 formed by spirally winding a full band strip. The full band 80 is situated between the inside belt ply 92 and the outside belt ply 94. The full band strip is cord arrangement body on which a plurality of band cords 84F are arranged. The number of the band cords 84F which are contained in the full band strip is two or more and five or less.SELECTED DRAWING: Figure 2A

Description

[Technical Field]

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

[0002] Tires undergo repeated deformation and recovery while in operation. Heavy-duty tires tend to grow in outer diameter, which affects uneven wear resistance and durability.

[0003] The band is one of the elements that make up the tire. The band includes a band cord that extends substantially in the circumferential direction. The band can contribute to suppressing the growth of the outer diameter due to running. In order to suppress the growth of the outer diameter and improve uneven wear resistance and durability, the use of a band has been considered (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2022-047999 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a heavy-duty tire that can achieve improved resistance to uneven wear and durability. [Means for solving the problem]

[0006] The heavy-duty tire according to the present invention comprises a pair of beads, a carcass spanning the pair of beads, a tread located radially outward of the carcass and having a tread surface in contact with the road surface, and a reinforcing layer located radially between the carcass and the tread. The reinforcing layer comprises a belt including a large number of parallel belt cords and a band including a spirally wound band cord. The belt comprises an inner belt ply and an outer belt ply aligned radially. The belt cords included in the inner belt ply have an inclination direction opposite to the inclination direction of the belt cords included in the outer belt ply. The band comprises a full band formed by spirally winding a full band strip. The full band is located between the inner belt ply and the outer belt ply. The full band strip is a cord arrangement in which a plurality of the band cords are arranged. The number of the band cords included in the full band strip is between two and five. [Effects of the Invention]

[0007] The present invention can provide a heavy-duty tire that can achieve improved resistance to uneven wear and durability. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view showing a portion of a heavy-duty tire according to one embodiment of the present invention. [Figure 2A] FIG. 2 is an enlarged cross-sectional view showing a portion of the tire of FIG. 1. [Figure 2B] FIG. 2B is an enlarged cross-sectional view showing part B of FIG. 2A. [Figure 2C] FIG. 2B is an enlarged cross-sectional view showing part C in FIG. 2A. [Figure 3] FIG. 4 is a cross-sectional view of a circumferential groove. [Figure 4] FIG. 2 is a schematic diagram illustrating the configuration of a reinforcing layer. [Figure 5] FIG. 2 is a perspective view showing a portion of a full band strip. [Figure 6] FIG. 2 is a perspective view showing a portion of an edgeband strip. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, the present invention will be described in detail based on preferred embodiments, with appropriate reference to the drawings.

[0010] The tire of the present invention is mounted on a rim. The inside of the tire is filled with air, and the internal pressure of the tire is adjusted. A tire mounted on a rim is also called a tire-rim assembly. A tire-rim assembly includes a rim and a tire mounted on the rim.

[0011] In the present invention, the 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 the standard state.

[0012] 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 of the tire's meridian cross section, which cannot be measured when the tire is mounted on a regular rim, are measured on a cut surface of the tire obtained by cutting the tire along a plane including the rotation axis. In this measurement, the tire is set so that the distance between the left and right beads matches the distance between the beads of the tire mounted on a regular rim. Note that the tire configuration, which cannot be confirmed when the tire is mounted on a regular rim, is confirmed on the cut surface.

[0013] A genuine rim is a rim 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 all genuine rims.

[0014] Normal tire pressure refers to the pressure specified in the standard on which the tire is based. The "maximum tire pressure" in the JATMA standard, the "maximum tire pressure" listed in the TRA standard's "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURE" and the "INFLATION PRESSURE" in the ETRTO standard are normal tire pressures.

[0015] 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 the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "LOAD CAPACITY" in the ETRTO standard are normal loads.

[0016] In the present invention, the "nominal aspect ratio" is the "nominal aspect ratio" included in the "tire designation" specified in JIS D4202 "Automobile tires - designations and specifications."

[0017] In the present invention, the number of cords contained per 50 mm width of a tire element containing parallel cords is expressed as the cord density (unit: ends / 50 mm). Unless otherwise specified, the cord density is obtained on a cross section of the element obtained by cutting the element in a plane perpendicular to the longitudinal direction of the cord. Since an element containing a spirally wound cord also has a plurality of cords that appear to be parallel, the cord density can be obtained in the same manner as for a tire element containing parallel cords.

[0018] In the present invention, the tread portion of a tire is the portion of the tire that comes into contact with the road surface. The bead portion is the portion of the tire that fits onto the rim. The sidewall portion is the portion of the tire that bridges between the tread portion and the bead portion. A tire has the following portions: a tread portion, a pair of bead portions, and a pair of sidewall portions. The center of the tread is also called the crown, and the edges of the tread are also called the shoulders.

[0019] [Findings that form the basis of the present invention] The belt includes a plurality of belt plies arranged in the radial direction. When a full band is used as a band to be combined with the belt in order to suppress growth of the outer diameter during running, the full band is laminated on the belt plies.

[0020] In low-profile tires with an aspect ratio of 65% or less, the growth in outer diameter of the shoulder area is greater than that of the crown area. Therefore, in order to restrict movement in the shoulder area, the use of edge bands in addition to full bands is also considered for low-profile tires. In this case, the edge bands are placed radially outward from the ends of the full bands.

[0021] The band includes a spirally wound band cord. Band strips are used to form the band. Band strips used to form full bands are also called full band strips, and band strips used to form edge bands are also called edge band strips.

[0022] The band strip includes one or more band cords. When the band strip includes more than one band cord, the more than one band cord is arranged in the width direction in the band strip. From the viewpoint of tire productivity, a cord arrangement in which 9 or 10 band cords are arranged is used as the band strip.

[0023] In order to establish a technology that can suppress outer diameter growth due to running, the inventors investigated the effects of band strips and found that the fewer the number of band cords included in the band strip, the more the outer diameter growth is suppressed, but the distance between the band cord and the belt cord tends to become shorter, and that, particularly when the band strip includes only one band cord, there is a risk of contact between the band cord and the belt cord (hereinafter referred to as cord touch). Placing a rubber sheet between the belt ply and the full band can prevent cord touch. However, in this case, a step of placing the rubber sheet between the belt ply and the full band is added to the tire manufacturing method, which reduces tire productivity.

[0024] Therefore, in order to obtain a heavy-duty tire that can achieve improved resistance to uneven wear and durability, the inventors conducted extensive research aimed at establishing a technology that can suppress growth in outer diameter due to running while preventing contact between the band cord and the belt cord, and have completed the present invention, which will be described below.

[0025] [Outline of the embodiment of the present invention] The present invention is a heavy-duty tire comprising: a pair of beads; a carcass spanning the pair of beads; a tread located radially outward of the carcass and having a tread surface that contacts the road surface; and a reinforcing layer located radially between the carcass and the tread, wherein the reinforcing layer comprises a belt including a large number of parallel belt cords and a band including a spirally wound band cord, the belt comprises an inner belt ply and an outer belt ply that are aligned radially, the belt cords included in the inner belt ply having an inclination direction opposite to the inclination direction of the belt cords included in the outer belt ply, the band comprising a full band formed by spirally winding a full band strip, the full band being located between the inner belt ply and the outer belt ply, the full band strip being a cord arrangement in which a plurality of the band cords are arranged, and the number of the band cords included in the full band strip is 2 to 5.

[0026] The heavy duty tire of the present invention can achieve improved resistance to uneven wear and durability. The mechanism by which the tire exhibits such effects has not been clarified, but is presumed to be as follows.

[0027] In the tire of the present invention, the reinforcing layer has a full band disposed between the inner belt ply and the outer belt ply, which can contribute to suppressing growth of the outer diameter due to running. Since the band cords included in the full band extend substantially in the circumferential direction and the belt cords included in the outer belt ply are arranged to intersect with the belt cords included in the inner belt ply, shear strain occurring in the rubber positioned between the band cords and the belt cords is reduced.The full band can continue to stably exert its function of suppressing outer diameter growth. Since the number of band cords included in the full band strip is five or less, the full band formed by spirally winding this full band strip can effectively contribute to suppressing the growth of the outer diameter. Since the number of band cords included in the full band strip is two or more, the occurrence of coat touch is also suppressed. This tire can suppress growth in outer diameter due to running while preventing contact between the band cord and the belt cord, and can achieve improved uneven wear resistance and durability. There is no need to place a rubber sheet between the full band and the inner belt ply to prevent cord touch. This tire can achieve improved uneven wear resistance and durability while suppressing a decrease in productivity.

[0028] Preferably, the number of the band cords included in the full band strip is 3. In this case, the tire can have improved uneven wear resistance and durability while minimizing a decrease in productivity.

[0029] Preferably, the band further comprises a pair of edge bands formed by spirally winding an edge band strip, the edge band strip being a cord arrangement in which a plurality of the band cords are arranged, and the pair of edge bands are each located radially outward of the end of the full band. In this case, the edge bands reinforce the portion where the end of the full band is located. In this tire, movement of the shoulder portion is effectively restrained. Since outer diameter growth is suppressed, this tire can improve uneven wear resistance and durability.

[0030] Preferably, the number of the band cords included in the edge band strip is equal to or greater than 2 and equal to or less than 5. In this case, the tire can have improved uneven wear resistance and durability while minimizing a decrease in productivity.

[0031] A tire tread comprises a base portion and a cap portion. When the base portion is made of cross-linked rubber for low heat buildup and the cap portion is made of cross-linked rubber for wear resistance, the base portion can contribute to reducing the rolling resistance of the tire. However, the base portion has inferior physical properties compared to the cap portion. From the viewpoints of uneven wear resistance and durability, it is preferable that the amount of base portion contained in the tread is small. As described above, conventional tires use a cord arrangement in which nine or ten band cords are arranged as a band strip. In contrast, in the tire of the present invention, the full band strip contains five or fewer band cords, which is fewer than the number of band cords in the band strip of a conventional tire. The restraining force of the full band is higher than that of a conventional tire. Because movement of the shoulder portion is restrained, this tire can maintain low rolling resistance even if the amount of the base portion is reduced. Reducing the amount of the base portion contributes to improved uneven wear resistance and durability. From the viewpoint of improving uneven wear resistance and durability, the tread preferably includes a base portion located radially outward of the reinforcing layer and a cap portion located radially outward of the base portion and having the tread surface, and the ratio of the thickness of the base portion to the thickness of the tire is 1 / 3 or less on a normal line of the carcass passing through the edge of the tread surface. In this case, the tire can maintain low rolling resistance while improving uneven wear resistance and durability.

[0032] As described above, according to the present invention, a heavy-duty tire can be obtained that can achieve improved resistance to uneven wear and durability. This will be explained in detail below using the heavy-duty tire shown in FIG. 1 as an example.

[0033] [Details of the embodiment of the present invention] 1 shows a part of a tire 2 according to one embodiment of the present invention. This tire 2 is mounted on vehicles such as trucks and buses. This tire 2 is a heavy-duty tire. The nominal aspect ratio of this tire 2 is 65% or less. In other words, this tire 2 has a nominal aspect ratio of 65% or less. This tire 2 is a low aspect tire.

[0034] FIG. 1 shows a part of a cross section (hereinafter referred to as a meridian cross section) of a tire 2 taken along a plane including the rotation axis of the tire 2. Fig. 2A shows a part of the cross section shown in Fig. 1. Fig. 2A shows the tread portion T of the tire 2. FIG. 2B shows the portion surrounded by the dotted line B in FIG. 2A (hereinafter, referred to as portion B). FIG. 2C shows the portion surrounded by the dotted line C in FIG. 2A (hereinafter, referred to as portion C).

[0035] The direction indicated by the double-headed arrow AD is the axial direction of the tire 2. The axial direction of the tire 2 means a direction parallel to the rotation axis of the tire 2. The direction indicated by the double-headed arrow RD 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. A dashed line EL extending in the radial direction represents the equatorial plane of the tire 2.

[0036] The direction from the equatorial plane toward the edge of the tread surface, which will be described later, is the outer side in the axial direction of the tire 2, and the direction from the edge of the tread surface toward the equatorial plane is the inner side in the axial direction of the tire 2. The direction indicated by the arrow RD1 is the radially outer side of the tire 2, and the direction indicated by the arrow RD2 is the radially inner side of the tire 2. The tire 2 shown in Figures 1 and 2 is mounted on a rim R (regular rim).

[0037] The tire 2 includes a tread 4, a pair of sidewalls 6, a pair of chafers 8, a pair of beads 10, a carcass 12, a pair of cushion layers 14, an inner liner 16, insulation 18, a pair of steel fillers 20, a pair of interlayer strips 22, and a reinforcing layer 24.

[0038] The tread 4 is located radially outward of the carcass 12. The tread 4 covers the reinforcing layer 24. The tread 4 has a tread surface 26 that comes into contact with the road surface. The tire 2 comes into contact with the road surface at the tread surface 26. The position indicated by the symbol TE is the edge of the tread surface 26. The width WT of the tread surface 26 is represented by the axial distance from one end TE of the tread surface 26 to the other end TE of the tread surface 26. In a tire, if the edge of the tread surface cannot be identified visually, the position on the outer surface of the tire corresponding to the axially outer edge of the contact patch obtained by applying a normal load to a tire in a normal state, setting the camber angle to 0°, and contacting the tire with a flat surface is used as the edge of the tread surface.

[0039] The intersection Eq of the tread surface 26 and the equatorial plane is the equator. If there are grooves on the equatorial plane, the equator is identified based on a virtual tread surface obtained assuming that there are no grooves.

[0040] The tread 4 comprises a base portion 28 and a cap portion 30. The base portion 28 is located radially outside the reinforcing layer 24. The base portion 28 covers the entire reinforcing layer 24. The base portion 28 is made of a low-heat-generating cross-linked rubber. The cap portion 30 is located radially outside the base portion 28. The cap portion 30 is made of a cross-linked rubber that takes into account wear resistance and grip performance. The cap portion 30 has a tread surface 26.

[0041] 1, the position indicated by the symbol BE is the radially inner end of the base portion 28. The position indicated by the symbol CE is the radially inner end of the cap portion 30. The inner end CE of the cap portion 30 is located radially inside the inner end BE of the base portion 28. The inner end BE of the base portion 28 is covered by the cap portion 30. The cap portion 30 covers the entire base portion 28. The inner end CE of the cap portion 30 is the radially inner end TRE of the tread 4. The inner end TRE of the tread 4 is located between the sidewall 6 and the cushion layer 14.

[0042] Grooves 32 are cut into the tread 4, thereby forming a tread pattern. The tread pattern of the tread 4 of this tire 2 has a plurality of circumferential grooves 34 that extend continuously in the circumferential direction. This tread 4 has four circumferential grooves 34. These circumferential grooves 34 are aligned in the axial direction and extend straight in the circumferential direction. The cross section of the circumferential groove 34 shown in Figures 1 and 2 corresponds to a cross section taken along a plane perpendicular to the length direction of the circumferential groove 34.

[0043] Fig. 3 shows a portion of the tire 2 shown in Fig. 2A. Fig. 3 shows a cross section of a circumferential groove 34, specifically, a shoulder circumferential groove, which will be described later. The main configuration of the groove 32 will be described based on the cross section of the circumferential groove 34 shown in Fig. 3. The groove 32 has a pair of groove walls 32W that bridge between the groove mouth 32M and the groove bottom 32T. In the groove 32, the portion including the groove bottom 32T is also referred to as the bottom surface 32B. Of the groove walls 32W, the portion other than the bottom surface 32B, i.e., the portion between the bottom surface 32B and the groove mouth 32M, is also referred to as the wall surface 32S. The groove 32 has a pair of wall surfaces 32S that include the groove mouth 32M, and the bottom surface 32B that includes the groove bottom 32T.

[0044] The groove bottom 32T is the deepest position in the cross section of the groove 32. The distance from a plane including the left and right edges 32E that form the groove opening 32M to the bottom surface 32B is measured along the normal to this plane. The position where the distance from this plane to the bottom surface 32B is greatest is the groove bottom 32T. The direction of the normal to the plane including the left and right edges 32E is the depth direction of the groove 32. The bottom surface 32B shown in Figure 3 is a curved surface. This bottom surface 32B may be configured as a flat surface. In this case, the width center of the flat surface configuring the bottom surface 32B is used as the groove bottom 32T. If a protrusion is provided on the bottom surface 32B, the groove bottom 32T is identified based on a virtual bottom surface obtained assuming that the protrusion does not exist.

[0045] In FIG. 3, the length indicated by the double-headed arrow WG is the groove width of the groove 32 at the groove opening 32M. The groove width WG is measured along a plane including a pair of edges 32E that form the groove opening 32M. If the groove opening 32M of the groove 32 is tapered, the groove width at the groove opening 32M of the groove 32 is expressed based on a virtual edge obtained by assuming that the groove is not tapered. The length indicated by the double-headed arrow DG is the groove depth of the groove 32. The groove depth DG of the groove 32 is expressed as the shortest distance from the plane including the left and right edges 32E to the groove bottom 32T of the groove 32.

[0046] The four circumferential grooves 34 have a wide groove width, and a pair of wall surfaces 34S of the circumferential grooves 34 do not come into contact with each other even when the tread 4 comes into contact with the road surface and deforms, and are also called circumferential main grooves. From the viewpoint of contributing to drainage performance and traction performance, the groove width WGC of the circumferential grooves 34 is preferably 2% to 10% of the width WT of the tread surface 26.

[0047] As described above, the tread 4 of the tire 2 has four circumferential grooves 34 . In the present invention, of the multiple circumferential grooves cut in the tread, the circumferential groove located at the outermost position in the axial direction is a shoulder circumferential groove. A circumferential groove located on the equatorial plane is a center circumferential groove. When no circumferential groove is provided on the equatorial plane, the circumferential groove closest to the equatorial plane is the center circumferential groove. When a circumferential groove is located between the center circumferential groove and the shoulder circumferential groove, the circumferential groove located between the center circumferential groove and the shoulder circumferential groove is called a middle circumferential groove.

[0048] In this tire 2, of the four circumferential grooves 34 formed in the tread 4, the circumferential grooves 36 located on the outermost side in the axial direction are shoulder circumferential grooves. The circumferential groove 38 closest to the equatorial plane is a center circumferential groove. The four circumferential grooves 34 include a pair of center circumferential grooves 38 and a pair of shoulder circumferential grooves 36. The shoulder circumferential grooves 36 are located axially outward of the center circumferential grooves 38.

[0049] A plurality of circumferential grooves 34 are formed in the tread 4, and a plurality of land portions 40 are arranged in the axial direction. In other words, the tread 4 has a plurality of circumferential grooves 34, and the plurality of circumferential grooves 34 form a plurality of land portions 40 in the tread 4. Four circumferential grooves 34 are formed in the tread 4 of this tire 2, and five land portions 40 are formed. These land portions 40 are aligned in the axial direction.

[0050] In the present invention, the land portion located at the outermost position in the axial direction among the multiple land portions configured in the tread is called a shoulder land portion. A land portion located on the equatorial plane is called a center land portion. If no land portion is provided on the equatorial plane, the land portion closest to the equatorial plane is called a center land portion. If a land portion is located between a center land portion and a shoulder land portion, this land portion between the center land portion and the shoulder land portion is called a middle land portion.

[0051] As described above, the tread 4 is configured with five land portions 40. Of the five land portions 40, the land portion 42 located on the outermost side in the axial direction is the shoulder land portion. The land portion 44 located on the equatorial plane is the center land portion. The land portion 46 located between the center land portion 44 and the shoulder land portion 42 is the middle land portion. The five land portions 40 include a center land portion 44, a pair of middle land portions 46, and a pair of shoulder land portions 42. The middle land portions 46 are located axially outward of the center land portion 44. The shoulder land portions 42 are located axially outward of the middle land portions 46. The shoulder land portions 42 include the edges TE of the tread surface 26.

[0052] The axial width of the center land portion 44 is 10% to 18% of the width WT of the tread surface 26. The axial width of the middle land portion 46 is 10% to 18% of the width WT of the tread surface 26. The axial width of the shoulder land portion 42 is 15% to 25% of the width WT of the tread surface 26. The axial width of the land portion 40 is represented by the axial width of the top surface of the land portion 40 that forms part of the tread surface 26.

[0053] Each sidewall 6 is continuous with an end of the tread 4. The sidewall 6 is located axially outward of the carcass 12. The sidewall 6 is made of crosslinked rubber.

[0054] Each chafer 8 is located radially inward of the sidewall 6. The chafers 8 come into contact with the rim R. The chafers 8 are made of crosslinked rubber in consideration of wear resistance.

[0055] Each bead 10 is located axially inward of the chafer 8. The beads 10 are located radially inward of the sidewall 6.

[0056] The bead 10 includes a core 48 and an apex 50 . The core 48 extends in the circumferential direction and includes a wound steel wire, not shown. The apex 50 is located radially outward from the core 48. The apex 50 extends radially outward from the core 48. The apex 50 tapers outward. The apex 50 includes an inner apex 52 and an outer apex 54. The inner apex 52 is located radially outward of the core 48. The outer apex 54 is located radially outward of the inner apex 52. The inner apex 52 is tapered outward and is made of hard cross-linked rubber. The outer apex 54 is thick near the radially outer end of the inner apex 52. From this thickened portion, the outer apex 54 tapers inward and then outward. The outer apex 54 is made of cross-linked rubber and is softer than the inner apex 52.

[0057] The carcass 12 is located inside the tread 4, the pair of sidewalls 6, and the pair of chafers 8. The carcass 12 bridges between the pair of beads 10. The carcass 12 of the tire 2 has a radial structure.

[0058] The carcass 12 includes at least one carcass ply 56. The carcass 12 of the tire 2 is configured with one carcass ply 56. The carcass ply 56 is turned up at each bead 10.

[0059] The carcass ply 56 includes a ply body 58 and a pair of turned-up portions 60. The ply body 58 spans between a pair of beads 10, i.e., between a first bead 10 and a second bead 10 (not shown). Each turned-up portion 60 is continuous with the ply body 58 and turned up at the bead 10. The turned-up portions 60 of this tire 2 are turned up at the bead 10 from the inside toward the outside in the axial direction.

[0060] The carcass ply 56 includes a large number of carcass cords 62 arranged in parallel. These carcass cords 62 are covered with a topping rubber 64. Each carcass cord 62 intersects with the equatorial plane. The angle that the carcass cord 62 makes with respect to the equatorial plane is equal to or greater than 70° and equal to or less than 90°. The carcass cords 62 of this tire 2 are steel cords.

[0061] In Fig. 2B, the dashed dotted line CL is the center line of the carcass cord 62. The outline of the carcass 12, in other words, the case line, is represented by the center line of the carcass cord 62 included in the ply body 58. The normal line of the carcass 12, which will be described later, is represented by the normal line of the case line CL. When the carcass 12 is made up of two or more carcass plies 56, the case line CL is represented by the center line of the carcass cord 62 included in the ply body 58 located outermost.

[0062] Each cushion layer 14 is located at an end of the reinforcing layer 24 between the reinforcing layer 24 and the carcass 12. The cushion layer 14 is made of a soft crosslinked rubber.

[0063] The inner liner 16 is located 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 a low gas permeability coefficient. The inner liner 16 maintains the internal pressure of the tire 2.

[0064] The insulation 18 is located between the carcass 12 and the inner liner 16. The insulation 18 is bonded to the carcass 12 and to the inner liner 16. In other words, the inner liner 16 is bonded to the carcass 12 via the insulation 18. The insulation 18 is made of crosslinked rubber with adhesive properties taken into consideration.

[0065] Each steel filler 20 is located between the carcass 12 and the chafer 8. The steel filler 20 is folded back at the bead 10 along the carcass ply 56. The steel filler 20 is arranged so as to wrap around the radially inner portion of the bead 10 from the radially inner side of the carcass 12. The inner end 20N of the steel filler 20 is located radially between the outer end of the inner apex 52 and the core 48. The outer end 20G of the steel filler 20 is located radially between the end of the turned-up portion 60 and the core 48.

[0066] Although not shown, the steel filler 20 includes a number of filler cords arranged in parallel. These filler cords are covered with a topping rubber. The filler cords of this tire 2 are steel cords.

[0067] Each interlayer strip 22 is located axially between the apex 50 and the chafer 8. The interlayer strip 22 covers the end of the folded portion 60 and the outer end 20G of the steel filler 20. The interlayer strip 22 is made of crosslinked rubber.

[0068] The reinforcing layer 24 is located radially outside the carcass 12. The reinforcing layer 24 is located radially inside the tread 4. The reinforcing layer 24 is located radially between the carcass 12 and the tread 4. The reinforcing layer 24 includes a belt 66 and a band 68.

[0069] Fig. 4 shows the configuration of the reinforcing layer 24. The direction indicated by the double arrow CD is the circumferential direction of the tire 2. The direction perpendicular to the paper surface of Fig. 4 is the radial direction of the tire 2. The front side of the paper surface is the radially outer side, and the back side is the radially inner side.

[0070] The belt 66 includes at least two belt plies 70 arranged in the radial direction. Each belt ply 70 is arranged such that both ends 70e of the belt ply 70 face each other across the equator plane. Each belt ply 70 intersects with the equator plane. The belt 66 of the tire 2 includes four belt plies 70. The four belt plies 70 are a first belt ply 70A, a second belt ply 70B, a third belt ply 70C, and a fourth belt ply 70D. The number of belt plies 70 constituting the belt 66 may be two or three.

[0071] The first belt ply 70A is the belt ply 70 located radially innermost among the four belt plies 70 that constitute the belt 66. The second belt ply 70B is located radially outer than the first belt ply 70A. The third belt ply 70C is located radially outer than the second belt ply 70B. The fourth belt ply 70D is located radially outer than the third belt ply 70C. The fourth belt ply 70D is the belt ply 70 located radially outermost among the four belt plies 70 that constitute the belt 66.

[0072] As shown in Fig. 1, a first belt ply 70A of the tire 2 is laminated on the carcass 12. A second belt ply 70B is laminated on the first belt ply 70A. A fourth belt ply 70D is laminated on a third belt ply 70C. A full band, which will be described later, is disposed between the second belt ply 70B and the third belt ply 70C of the tire 2.

[0073] In the tire 2, the second belt ply 70B has the widest axial width and the fourth belt ply 70D has the narrowest axial width. The first belt ply 70A and the third belt ply 70C have the same axial width, or the axial width of the first belt ply 70A is slightly narrower than the axial width of the third belt ply 70C.

[0074] In the present invention, the edge of the belt is represented by the edge of the belt ply having the widest axial width among the plurality of belt plies constituting the belt. As described above, the second belt ply 70B has the widest axial width in the tire 2. The end 66e of the belt 66 of the tire 2 is represented by the end 70Be of the second belt ply 70B. The end 66e of the belt 66 is also the end 24e of the reinforcing layer 24.

[0075] 2A , an end 70Ae of the first belt ply 70A is located axially outward from the shoulder circumferential groove 36. An end 70Be of the second belt ply 70B is also located axially outward from the shoulder circumferential groove 36. An end 70Ce of the third belt ply 70C is also located axially outward from the shoulder circumferential groove 36. An end 70De of the fourth belt ply 70D is also located axially outward from the shoulder circumferential groove 36. In the tread portion T shown in FIG. 2A , the ends 70e of all belt plies 70 constituting the belt 66 are located axially outward from the shoulder circumferential groove 36. The end 70De of the fourth belt ply 70D may be disposed axially inward from the shoulder circumferential groove 36.

[0076] In FIG. 1, the length indicated by the double arrow W1 is the axial width of the first belt ply 70A. The length indicated by the double arrow W2 is the axial width of the second belt ply 70B. The length indicated by the double arrow W3 is the axial width of the third belt ply 70C. The length indicated by the double arrow W4 is the axial width of the fourth belt ply 70D. The axial width of each belt ply 70 is represented by the axial distance from one end 70e of the belt ply 70 to the other end 70e.

[0077] In this tire 2, from the viewpoint of ensuring the rigidity of the tread portion T, the ratio (W1 / WT) of the axial width W1 of the first belt ply 70A to the width WT of the tread surface 26 is preferably 0.80 or more and 0.90 or less. The ratio (W2 / WT) of the axial width W2 of the second belt ply 70B to the width WT of the tread surface 26 is preferably 0.85 or more and 0.95 or less. The ratio (W3 / WT) of the axial width W3 of the third belt ply 70C to the width WT of the tread surface 26 is preferably 0.80 or more and 0.90 or less. The axial width W4 of the fourth belt ply 70D is set appropriately depending on the specifications of the tire 2.

[0078] 4, each belt ply 70 constituting the belt 66 includes a large number of parallel belt cords 72. For ease of explanation, the belt cords 72 are represented by solid lines, and the belt cords 72 are covered with a topping rubber 74. The belt cords 72 of the tire 2 are steel cords. The cord density of each belt ply 70 is 15 ends / 50 mm or more and 30 ends / 50 mm or less.

[0079] In each belt ply 70, the belt cords 72 are inclined with respect to the circumferential direction. The inclination direction of the belt cords 72 included in the first belt ply 70A (hereinafter referred to as the inclination direction of the first belt cords 72A) is the same as the inclination direction of the belt cords 72 included in the second belt ply 70B (hereinafter referred to as the inclination direction of the second belt cords 72B). The inclination direction of the second belt cord 72B is opposite to the inclination direction of the belt cord 72 included in the third belt ply 70C (hereinafter referred to as the inclination direction of the third belt cord 72C). The inclination direction of the third belt cord 72C is the same as the inclination direction of the belt cord 72 included in the fourth belt ply 70D (hereinafter referred to as the inclination direction of the fourth belt cord 72D). The inclination direction of the first belt cord 72A may be opposite to the inclination direction of the second belt cord 72B. The inclination direction of the third belt cord 72C may be opposite to the inclination direction of the fourth belt cord 72D.

[0080] In Fig. 4, angle θ1 is the angle that the first belt cord 72A makes with respect to the equatorial plane (hereinafter referred to as the first inclination angle θ1). Angle θ2 is the angle that the second belt cord 72B makes with respect to the equatorial plane (hereinafter referred to as the second inclination angle θ2). Angle θ3 is the angle that the third belt cord 72C makes with respect to the equatorial plane (hereinafter referred to as the third inclination angle θ3). Angle θ4 is the angle that the fourth belt cord 72D makes with respect to the equatorial plane (hereinafter referred to as the fourth inclination angle θ4).

[0081] The first inclination angle θ1, the second inclination angle θ2, the third inclination angle θ3, and the fourth inclination angle θ4 are preferably equal to or greater than 10 degrees and equal to or less than 60 degrees. From the viewpoint of effectively restricting the movement of the tread portion T and obtaining a stable contact patch with minimal shape change, the first inclination angle θ1 is more preferably 40 degrees or greater and 60 degrees or less. The second inclination angle θ2 is more preferably 15 degrees or greater and 30 degrees or less, and even more preferably 15 degrees or greater and 20 degrees or less. The third inclination angle θ3 is more preferably 15 degrees or greater and 30 degrees or less, and even more preferably 15 degrees or greater and 20 degrees or less. The fourth inclination angle θ4 is more preferably 15 degrees or greater and 50 degrees or less.

[0082] As shown in FIG. 2A , the end 70Be of the second belt ply 70B and the end 70Ce of the third belt ply 70C are each covered with a rubber layer 76. Three more rubber layers 76 are disposed between the end 70Be of the second belt ply 70B and the end 70Ce of the third belt ply 70C, which are covered with the rubber layer 76. In the tire 2, an edge member 78 made of a total of five rubber layers 76 is configured between the end 70Be of the second belt ply 70B and the end 70Ce of the third belt ply 70C. The edge member 78 is made of crosslinked rubber. The edge member 78 contributes to maintaining the distance between the end 70Be of the second belt ply 70B and the end 70Ce of the third belt ply 70C. In the tire 2, change in the positional relationship between the end 70Be of the second belt ply 70B and the end 70Ce of the third belt ply 70C due to running is suppressed. The edge member 78 is a part of the reinforcing layer 24. The reinforcing layer 24 of the tire 2 includes a pair of edge members 78 in addition to the belt 66 and the band 68 .

[0083] The band 68 includes a full band 80. The full band 80 is disposed so that both ends 80e thereof face each other across the equatorial plane. The full band 80 intersects with the equatorial plane. The end 80e of the full band 80 is located between the shoulder circumferential groove 36 and the end 66e of the belt 66 in the axial direction.

[0084] 1, the length indicated by the double-headed arrow WF is the axial width of the full band 80. The axial width WF of the full band 80 is expressed as the axial distance from one end 80e to the other end 80e of the full band 80. From the viewpoint of ensuring the rigidity of the tread portion T, the ratio of the axial width WF of the full band 80 to the width WT of the tread surface 26 (WF / WT) is preferably 0.70 or more and 0.80 or less.

[0085] The band 68 of the tire 2 may include a pair of edge bands 82 in addition to the full band 80. The pair of edge bands 82 are arranged spaced apart in the axial direction across the equatorial plane. Each of the pair of edge bands 82 is located axially outward of the fourth belt ply 70D. The edge bands 82 are located axially between the shoulder circumferential groove 36 and the end 66e of the belt 66. The edge bands 82 are located radially between the tread 4 and the full band 80.

[0086] 4, the full band 80 and the edge band 82 that make up the band 68 each include a spirally wound band cord 84. For ease of explanation, the band cord 84 is represented by a solid line, and the band cord 84 is covered with a topping rubber 86. The band cord 84 extends substantially in the circumferential direction in each of the full band 80 and the edge band 82. Specifically, the angle that the band cord 84 forms with the circumferential direction is preferably 5° or less, and more preferably 2° or less.

[0087] The band cords 84 of this tire 2 are steel cords. Cords made of organic fibers (hereinafter referred to as organic fiber cords) may be used as the band cords 84. In this case, examples of the organic fibers include nylon fibers, polyester fibers, rayon fibers, and aramid fibers. The band cords 84F of the full band 80 and the band cords 84E of the edge band 82 may be the same cord or different cords. The band cords 84 used for the full band 80 and the edge band 82 are determined depending on the specifications of the tire 2.

[0088] 1 is manufactured by a known manufacturing method. An unvulcanized tire 2, i.e., a green tire (not shown), is prepared by combining components such as a tread 4 and a sidewall 6. The green tire is then pressurized and heated in a mold to obtain the tire 2.

[0089] The band 68 is formed using a band strip 88. Figure 5 shows a band strip 88 used to form the full band 80 (hereinafter referred to as a full band strip 88F). The full band strip 88F is belt-shaped. The full band strip 88F includes a plurality of band cords 84F. The full band strip 88F shown in FIG. 5 includes three band cords 84F. These band cords 84F are aligned in the width direction of the full band strip 88F and extend in the length direction of the full band strip 88F. The full band strip 88F is a cord arrangement in which a plurality of band cords 84F are arranged. In the full band strip 88F, the distance between adjacent band cords 84F is 0.5 mm or more and 2.0 mm or less.

[0090] 6 shows a band strip 88 (hereinafter referred to as edge band strip 88E) used to form the edge band 82. The edge band strip 88E has a configuration similar to that of the full band strip 88F. The edge band strip 88E is a cord arrangement in which a plurality of band cords 84E are arranged. In the edge band strip 88E, the interval between adjacent band cords 84E is 0.5 mm or more and 2.0 mm or less.

[0091] The band 68 is formed by spirally winding a band strip 88. Specifically, the band 68 is a cross-linked product of a band molding formed by spirally winding the band strip 88. The full band 80 is a component of the tire 2 formed by spirally winding a full band strip 88F. The edge band 82 is a component of the tire 2 formed by spirally winding an edge band strip 88E. The band 68 of this tire 2 includes a full band 80 formed by spirally winding a full band strip 88F, and a pair of edge bands 82 formed by spirally winding an edge band strip 88E.

[0092] In this tire 2, the full band strip 88F and the edge band strip 88E have the same configuration. The full band strip 88F and the edge band strip 88E may have different configurations.

[0093] The full band 80 of the tire 2 is located between the second belt ply 70B and the third belt ply 70C. The second belt ply 70B is located radially inside the full band 80, and the third belt ply 70C is located radially outside the full band 80. As described above, the inclination direction of the second belt cord 72B is opposite to the inclination direction of the third belt cord 72C. The full band 80 is located between two belt plies 70 in which the inclination directions of the belt cords 72 are opposite to each other.

[0094] In the present invention, when a full band is positioned between two belt plies whose belt cords have inclination directions opposite to each other, the belt ply positioned radially inside the full band is called an inner belt ply, and the belt ply positioned radially outside the full band is called an outer belt ply.

[0095] In the tire 2, the full band 80 is located between the second belt ply 70B and the third belt ply 70C, and the inclination direction of the second belt cords 72B is opposite to the inclination direction of the third belt cords 72C. The second belt ply 70B is the inner belt ply 92, and the third belt ply 70C is the outer belt ply 94. In other words, the full band 80 is located between the inner belt ply 92 and the outer belt ply 94, and the inclination direction of the belt cords 72 included in the inner belt ply 92 is opposite to the inclination direction of the belt cords 72 included in the outer belt ply 94. If the full band 80 is located between the first belt ply 70A and the second belt ply 70B and the inclination direction of the first belt cord 72A is opposite to the inclination direction of the second belt cord 72B, the first belt ply 70A is the inner belt ply and the second belt ply 70B is the outer belt ply. If the full band 80 is located between the third belt ply 70C and the fourth belt ply 70D and the inclination direction of the third belt cord 72C is opposite to the inclination direction of the fourth belt cord 72D, the third belt ply 70C is the inner belt ply and the fourth belt ply 70D is the outer belt ply.

[0096] In the tire 2, the full band 80 is disposed between the inner belt ply 92 and the outer belt ply 94 in the reinforcing layer 24. The reinforcing layer 24 can contribute to suppressing growth in outer diameter due to running. The band cords 84F included in the full band 80 extend substantially in the circumferential direction, and the belt cords 72 included in the outer belt ply 94 are arranged to intersect with the belt cords 72 included in the inner belt ply 92, thereby reducing shear strain generated in the rubber located between the band cords 84F and the belt cords 72. The full band 80 can continue to stably exert its function of suppressing outer diameter growth. The number of band cords 84F included in the full band strip 88F of this tire 2 is 2 or more and 5 or less.

[0097] Since the number of band cords 84F included in the full band strip 88F is five or less, each band cord 84F can effectively restrain the movement of the tread portion T that tends to expand outward due to the action of the internal pressure and centrifugal force of the tire 2, compared to when a cord arrangement in which nine or ten band cords are arranged is used as the full band strip. The full band 80 formed by spirally winding this full band strip 88F can effectively contribute to suppressing growth in outer diameter. From this perspective, it is preferable that the number of band cords 84F included in the full band strip 88F is four or less.

[0098] Since the number of band cords 84F included in the full band strip 88F is two or more, contact between the band cord 84F of the full band 80 and the belt cord 72B of the inner belt ply 92, that is, coat touch, which was a concern when the number of band cords included in the band strip was one, is also suppressed.

[0099] This tire 2 can suppress growth in outer diameter due to running while preventing contact between the band cord 84 and the belt cord 72. This tire 2 can achieve improvements in uneven wear resistance and durability. To prevent cord touch, the tire 2 does not need to have a rubber sheet disposed between the full band 80 and the inner belt ply 92. The tire 2 can achieve improved uneven wear resistance and durability while suppressing a decrease in productivity. From this viewpoint, it is more preferable that the number of band cords 84F included in the full band strip 88F is three.

[0100] 2A , an end 92e of the inner belt ply 92 is located axially outward of an end 80e of the full band 80. An end 94e of the outer belt ply 94 is also located axially outward of the end 80e of the full band 80. The inner belt ply 92 and the outer belt ply 94 have an axial width that is wider than the axial width WF of the full band 80 that is located between the inner belt ply 92 and the outer belt ply 94.

[0101] The inner belt ply 92 and the outer belt ply 94 can effectively suppress the force acting on the full band 80. Since fluctuations in tension occurring in the band cords 84F of the full band 80 are suppressed to a small level, the full band 80 can stably perform its function. From this viewpoint, it is preferable that the inner belt ply 92 and the outer belt ply 94 have an axial width wider than the axial width WF of the full band 80 located between the inner belt ply 92 and the outer belt ply 94. It is preferable that the ratio WF / W3 of the axial width WF of the full band 80 to the axial width W3 of the outer belt ply 94, i.e., the axial width W3 of the third belt ply 70C, is 0.80 or more and 0.90 or less.

[0102] As described above, the inner belt ply 92 is the second belt ply 70B that has the widest axial width among the belt plies 70 that constitute the belt 66. From the viewpoint of improving uneven wear resistance, when the belt 66 is constituted by a plurality of belt plies 70 that are arranged in the radial direction, it is preferable that the belt ply 70 that has the widest axial width among the plurality of belt plies 70 that constitute the belt 66 is the inner belt ply 92.

[0103] As described above, the band 68 of the tire 2 can include a pair of edge bands 82 in addition to the full band 80 . 2A , the edge band 82 is located radially outward of the full band 80. The inner end 82ue of the edge band 82 is located axially inward of the end 80e of the full band 80. The outer end 82se of the edge band 82 is located axially outward of the end 80e of the full band 80. The edge band 82 overlaps with the end 80e of the full band 80 in the radial direction. In other words, the edge band 82 is located radially outward of the end 80e of the full band 80. The edge band 82 of the tire 2 reinforces the portion where the end 80e of the full band 80 is located. In the tire 2, movement of the shoulder portion is effectively restricted. Since growth in outer diameter is suppressed, the tire 2 can improve uneven wear resistance and durability. From this viewpoint, it is preferable that the band 68 of the tire 2 includes a pair of edge bands 82, and that each of the pair of edge bands 82 is located radially outward of the end 80e of the full band 80.

[0104] The edge band 82 is positioned radially outward of the outer belt ply 94. The outer belt ply 94 is positioned between the edge band 82 and the full band 80. As a result, the end 80e of the full band 80, whose movement is already restricted by sandwiching the full band 80 between the inner belt ply 92 and the outer belt ply 94, is further restricted by the edge band 82. Since fluctuations in tension occurring in the band cord 84F of the full band 80 are further suppressed, the full band 80 can perform its function more stably. From this viewpoint, it is preferable that the edge band 82 be positioned radially outward of the outer belt ply 94. In this case, it is more preferable that the edge band 82 be laminated on the outer belt ply 94, as shown in FIG. 2A .

[0105] The number of band cords 84E included in the edge band strip 88E of the tire 2 is preferably 2 or more and 5 or less.

[0106] By setting the number of band cords 84E included in the edge band strip 88E to five or less, each band cord 84E can effectively restrain the movement of the tread portion T that tends to expand outward due to the action of the internal pressure and centrifugal force of the tire 2, compared to when a cord arrangement in which nine or ten band cords are arranged is used as the edge band strip. The edge band 82 formed by spirally winding this edge band strip 88E can effectively contribute to suppressing growth in outer diameter. From this perspective, it is more preferable that the number of band cords 84E included in the edge band strip 88E be four or less.

[0107] By setting the number of band cords 84E included in the edge band strip 88E to two or more, contact between the band cord 84E of the edge band 82 and the belt cord 72C of the outer belt ply 94, i.e., coat touch, which is a concern when the number of band cords included in the band strip is one, is suppressed.

[0108] In this tire 2, in order to prevent the occurrence of cord touch, it is not necessary to dispose a rubber sheet not only between the full band 80 and the inner belt ply 92 but also between the edge band 82 and the outer belt ply 94. In this tire 2, it is possible to achieve improved uneven wear resistance and durability while suppressing a decrease in productivity. From this viewpoint, it is more preferable that the number of band cords 84E included in the edge band strip 88E is three. It is particularly preferable that the number of band cords 84F included in the full band strip 88F is three, and the number of band cords 84E included in the edge band strip 88E is three.

[0109] In Figure 1, the solid line NL is a normal to the carcass 12 that passes through the edge TE of the tread surface 26. The length indicated by the double arrow E is the thickness of the tire 2, measured along the normal line NL. As shown in Figure 1, the normal line NL intersects with the base portion 28. The length indicated by the double arrow B is the thickness of the base portion 28, measured along the normal line NL.

[0110] As described above, the tread 4 of this tire 2 includes a base portion 28 and a cap portion 30, with the base portion 28 being made of cross-linked rubber that takes into consideration low heat buildup, and the cap portion 30 being made of cross-linked rubber that takes into consideration wear resistance. The base portion 28 can contribute to reducing the rolling resistance of the tire 2, but is inferior in physical properties to the cap portion 30. Therefore, in order to improve the uneven wear resistance and durability of the tire 2, it is preferable that the amount of base portion 28 contained in the tread 4 is small. As described above, the full band strip 88F of this tire 2 includes five or fewer band cords, and therefore the full band 80 can contribute more effectively to restraining the movement of the tire 2 than a full band formed using a conventional band strip. Therefore, this tire 2 can maintain low rolling resistance even if the amount of the base portion 28 is reduced. Reducing the amount of the base portion 28 can contribute to improving uneven wear resistance and durability. From the viewpoint of improving uneven wear resistance and durability, the ratio B / E of the thickness B of the base portion 28 to the thickness E of the tire 2 on the normal line NL of the carcass 12 passing through the edge TE of the tread surface 26 is preferably 1 / 3 or less, and more preferably 1 / 5 or less. From the viewpoint of maintaining low rolling resistance, the ratio B / E is preferably 1 / 10 or more. In this case, the tire 2 can achieve improved uneven wear resistance and durability while maintaining low rolling resistance.

[0111] As shown in FIG. 1 , the end 24e of the reinforcing layer 24 is located axially inward of the normal line NL. Because the end 24e of the reinforcing layer 24 is located in an appropriate position, the end 24e of the reinforcing layer 24 is covered by a sufficient amount of the tread 4. In this tire 2, occurrence of damage such as belt edge loosening is effectively suppressed. The durability of this tire 2 can be improved. From this viewpoint, it is preferable that the end 24e of the reinforcing layer 24 is located axially inward of the normal line NL.

[0112] 2B, the length indicated by the double arrow FU is the distance between the full band 80 and the inner belt ply 92. The distance FU is expressed as the distance between the band cord 84F of the full band 80 that is closest to the end 80e of the full band 80 and the belt cord 72B of the inner belt ply 92 that is closest to this band cord 84F. The length indicated by the double arrow ES is the distance between the edge band 82 and the outer belt ply 94. The distance ES is expressed as the distance between the belt cord 72C of the outer belt ply 94, which is closest to the end 80e of the full band 80, and the band cord 84E of the edge band 82, which is closest to this belt cord 72C. Both the distance FU and the distance ES are the distance between the cords. These correspond to the thickness of the rubber component located between the band cord 84 and the belt cord 72. The rubber component corresponding to the distance FU is made up of the topping rubber 86 of the full band 80 and the topping rubber 74 of the inner belt ply 92. The rubber component corresponding to the distance ES is made up of the topping rubber 86 of the edge band 82 and the topping rubber 74 of the outer belt ply 94.

[0113] At the end 80e of the full band 80, the distance FU between the full band 80 and the inner belt ply 92 is preferably 0.6 mm or more. This effectively suppresses contact between the band cord 84F of the full band 80 and the belt cord 72B of the inner belt ply 92, i.e., the occurrence of cord touch. If the amount of rubber component located between the band cord 84F and the belt cord 72B is large, heat generation due to repeated deformation is promoted, which may result in an increase in the rolling resistance of the tire 2. From the viewpoint of suppressing an increase in rolling resistance, the distance FU is preferably 2.0 mm or less.

[0114] At the end 80e of the full band 80, the distance ES between the edge band 82 and the outer belt ply 94 is preferably 0.6 mm or more. This effectively suppresses contact between the band cords 84E of the edge band 82 and the belt cords 72C of the outer belt ply 94, i.e., the occurrence of cord touch. If the amount of rubber component located between the band cords 84E and the belt cords 72C is large, heat generation due to repeated deformation is promoted, which may result in an increase in the rolling resistance of the tire 2. From the viewpoint of suppressing an increase in rolling resistance, the distance ES is preferably 2.0 mm or less.

[0115] In FIG. 2A, the solid line LE is a straight line (hereinafter referred to as the inner edge reference line) that passes through the inner edge 82ue of the edge band 82 and extends radially. The position indicated by the symbol PE is the intersection of the inner edge reference line LE and the tread surface 26. This intersection PE is a position on the tread surface 26 that corresponds to the inner edge 82ue of the edge band 82 (hereinafter referred to as the inner edge corresponding position). The length indicated by the double arrow GE is the length from the shoulder circumferential groove 36 to the inner edge corresponding position PE. The length GE is expressed as the length measured along the tread surface 26 from the edge 36E of the shoulder circumferential groove 36 on the end TE side of the tread surface 26 to the inner edge corresponding position PE. The double-headed arrow WGCs indicates the groove width of the shoulder circumferential groove 36 at the groove opening 36M.

[0116] As described above, the edge band 82 of the tire 2 is located axially between the shoulder circumferential groove 36 and the end 66e of the belt 66. In other words, the edge band 82 is located within the shoulder land portion 42. If the edge band 82 is positioned near the shoulder circumferential groove 36, there is a concern that, despite the edge band 82 restraining movement of the shoulder portion, peculiar distortion will occur in the groove wall 36W of the shoulder circumferential groove 36, and depending on the degree of distortion, damage such as cracks will occur in the wall surface 36S or bottom surface 36B. Therefore, in this tire 2, the length GE from the shoulder circumferential groove 36 to the position PE corresponding to the inner end of the edge band 82 is controlled.

[0117] In the tire 2, the ratio GE / WGCs of the length GE from the shoulder circumferential groove 36 to the position PE corresponding to the inner end of the edge band 82 to the groove width WGCs of the shoulder circumferential groove 36 is preferably 0.30 or more and 0.50 or less. By setting the ratio GE / WGCs to 0.30 or more, the edge band 82 is disposed at an appropriate distance from the shoulder circumferential groove 36. In the tire 2, damage to the shoulder circumferential groove 36 caused by the edge band 82 can be suppressed. By setting the ratio GE / WGCs to 0.50 or less, the edge band 82 can effectively contribute to suppressing the growth of the outer diameter due to running.

[0118] A bottom surface 38B including a groove bottom 38T of the center circumferential groove 38 of the tire 2 is configured as a curved surface. In the cross section of the center circumferential groove 38 shown in FIG. 2A, the outline of the bottom surface 38B is represented by an arc. Arrow Rc in FIG. 2A indicates the radius of the arc representing the outline of the bottom surface 38B. A bottom surface 36B including a groove bottom 36T of the shoulder circumferential groove 36 is also configured as a curved surface. In the cross section of the shoulder circumferential groove 36 shown in FIG. 2A, the outline of the bottom surface 36B is represented by an arc. Arrow Rs in FIG. 2A indicates the radius of the arc representing the outline of the bottom surface 36B.

[0119] The radius Rc of the arc that defines the contour of the bottom surface 38B of the central circumferential groove 38 is preferably equal to or greater than 2.5 mm. This prevents unusual distortion from occurring on the bottom surface 38B of the central circumferential groove 38. This tire 2 can maintain good durability. From this viewpoint, the radius Rc is more preferably equal to or greater than 3.0 mm.

[0120] The radius Rs of the arc that defines the contour of the bottom surface 36B of the shoulder circumferential groove 36 is preferably equal to or greater than 2.5 mm. This prevents unusual distortion from occurring on the bottom surface 36B of the shoulder circumferential groove 36. This tire 2 can maintain good durability. From this viewpoint, the radius Rs is more preferably equal to or greater than 3.0 mm.

[0121] The length indicated by the double-headed arrow WGCs in FIG. 2A is the groove width of the shoulder circumferential groove 36 at the groove opening 36M. In this tire 2, when the radius Rs of the arc representing the outline of the bottom surface 36B of the shoulder circumferential groove 36 is 2.5 mm or more, the groove width WGCs at the groove opening 36M of the shoulder circumferential groove 36 is preferably 4% or more and 9% or less of the width WT of the tread surface 26. Setting the groove width WGCs to 4% or more of the width WT suppresses the occurrence of peculiar strain in the shoulder circumferential groove 36. This tire 2 can maintain good durability. By setting the groove width WGCs to 9% or less of the width WT, the size of the shoulder circumferential groove 36 is maintained appropriately, and the impact of the shoulder circumferential groove 36 on the rigidity of the tread portion T is suppressed. The tire 2 can effectively suppress the growth of the outer diameter due to running.

[0122] 2C is the distance between the outer belt ply 94 and the inner belt ply 92. The distance SU is expressed as the distance between the belt cord 72C of the outer belt ply 94 that is closest to the end 94e of the outer belt ply 94 and the belt cord 72B of the inner belt ply 92 that is closest to this belt cord 72C. The distance SU is the distance between the cords. The distance SU corresponds to the thickness of the rubber component located between the belt cord 72C and the belt cord 72B at the end 94e of the outer belt ply 94. The rubber component corresponding to the distance SU is made up of the topping rubber 74 of the outer belt ply 94, the edge member 78, and the topping rubber 74 of the inner belt ply 92.

[0123] At the end 94e of the outer belt ply 94, the distance SU between the outer belt ply 94 and the inner belt ply 92 is preferably 3.0 mm or more. The shoulder portion is prone to outer diameter growth during travel, and the end 66e of the belt 66 tends to experience unusual distortion. Depending on the degree of distortion, damage such as belt edge loosening may occur. However, by setting the distance SU to 3.0 mm or more, the occurrence of distortion is effectively suppressed. The tire 2 can maintain good durability. If the amount of rubber component located between the belt cord 72C and the belt cord 72B is large, there is a concern that heat generation due to repeated deformation will be promoted, resulting in an increase in the rolling resistance of the tire 2. From the viewpoint of suppressing an increase in rolling resistance, the distance SU is preferably 4.5 mm or less.

[0124] As is clear from the above description, according to the present invention, a heavy-duty tire 2 can be obtained that can achieve improved resistance to uneven wear and durability. Among heavy-duty tires, low-profile tires have a higher internal tread pressure distribution rate than high-profile tires, and are more likely to experience outer diameter growth in the shoulder area. This increases the ground contact pressure in the shoulder area, raising concerns that damage such as belt edge loosening may occur at the belt ends. Tires mounted on trailer axles are subjected to more axial force than tires mounted on other axles, which can cause specific strain in the shoulder area and lead to damage such as belt edge loosening at the ends of the belt. As described above, according to the present invention, the growth of the outer diameter due to running is suppressed, and the occurrence of distortion caused by this growth of the outer diameter is suppressed. In other words, by applying the present invention to a tire with a low aspect ratio that is mounted on a trailer axle, the occurrence of damage to the tire can be effectively suppressed. The present invention is particularly effective in a tire with a low aspect ratio that is mounted on a trailer axle. [Example]

[0125] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0126] [Examples 1-4 and Comparative Example 1] A heavy-duty pneumatic tire (tire size=355 / 50R22.5) having the basic configuration shown in FIG. 1 and the specifications shown in Table 1 below was obtained. The same band strip was used for the full band strip and the edge band strip. The number of band cords included in the band strip was changed as shown in Table 1 to obtain tires of Examples 1 to 4 and Comparative Examples 1 to 3.

[0127] [Outer diameter control] The prototype tire was mounted on a rim (size: 11.75 x 22.5), inflated, and the internal pressure of the tire was adjusted to the normal internal pressure. This tire was run for 1,000 km at a speed of 80 km / h in a drum testing machine, and the case line profile on the inside of the shoulder circumferential groove was obtained. This case line profile was compared with the case line profile before running to confirm the change in the profile before and after running. The results are shown in Table 1 below as an index, with the change in Comparative Example 2 set to 100. A larger value indicates greater suppression of outer diameter growth.

[0128] [Code Touch] The prototype tire was mounted on a rim (size: 11.75 x 22.5), inflated, and the internal pressure of the tire was adjusted to the standard internal pressure. This tire was run at a speed of 80 km / h on a drum testing machine. After running 1000 km, the distance FU between the full band and the inner belt ply was measured. The results are shown in Table 1 below as an index, with the distance FU of Comparative Example 2 set to 100. The larger the value, the more the occurrence of cord touch is suppressed.

[0129] [Productivity] The time required to form the band was measured. The results are shown in Table 1 below as an index, with the forming time of Comparative Example 2 set at 100. The larger the value, the shorter the forming time and the better the productivity.

[0130] [comprehensive evaluation] The indexes obtained from each evaluation were summed up. The results are shown in Table 1 below as an overall evaluation. The higher the value, the better.

[0131] [Table 1]

[0132] As shown in Table 1, in the example, the outer diameter control and the cord touch were well balanced, and the productivity was also excellent. From these evaluation results, the superiority of the present invention is clear. [Industrial Applicability]

[0133] The techniques described above that can achieve improvements in uneven wear resistance and durability can be applied to various tires.

[0134] [Note] The present invention includes the following aspects.

[0135] [1] A tire comprising: a pair of beads; a carcass spanning the pair of beads; a tread located radially outward of the carcass and having a tread surface in contact with the road surface; and a reinforcing layer located radially between the carcass and the tread, wherein the reinforcing layer comprises a belt including a large number of parallel belt cords and a band including a spirally wound band cord; the belt comprises an inner belt ply and an outer belt ply aligned radially, the belt cords included in the inner belt ply having an inclination direction opposite to the inclination direction of the belt cords included in the outer belt ply; the band comprises a full band formed by spirally winding a full band strip; the full band is located between the inner belt ply and the outer belt ply; the full band strip is a cord arrangement in which a plurality of the band cords are arranged; and the number of the band cords included in the full band strip is 2 to 5. [2] The heavy-duty tire according to the above-mentioned [1], wherein the number of the band cords included in the full band strip is three. [3] The heavy-duty tire according to [1] or [2] above, wherein the band further comprises a pair of edge bands formed by spirally winding an edge band strip, the edge band strip being a cord arrangement in which a plurality of the band cords are arranged, and the pair of edge bands are each located radially outward from the end of the full band. [4] The heavy-duty tire according to the above-mentioned [3], wherein the number of the band cords included in the edge band strip is 2 or more and 5 or less. [5] A heavy-duty tire according to any one of [1] to [4] above, wherein the tread comprises a base portion located radially outside the reinforcing layer, and a cap portion located radially outside the base portion and having the tread surface, and the ratio of the thickness of the base portion to the thickness of the tire is 1 / 3 or less on a normal line of the carcass passing through the edge of the tread surface. [Explanation of symbols]

[0136] 2. Tires 4. Tread 10 Bead 12. Carcass 24 Reinforcement layer 26 Tread surface 28 Base 30 Cap part 56···Carcass ply 58···Ply body 60... Folded part 62···Carcass cord 64···Carcass 12 topping rubber 66···Belt 68···Band 70, 92, 94... Belt plies 72 Belt cord 74 Belt 66 topping rubber 78 Edge member 80...Full Band 82 Edge band 84, 84F, 84E... Band cord 86···Band 68 topping rubber 88, 88F, 88E... Band Strip

Claims

1. A tire comprising: a pair of beads; a carcass spanning the pair of beads; a tread located radially outward of the carcass and having a tread surface in contact with a road surface; and a reinforcing layer located radially between the carcass and the tread, The reinforcing layer includes a belt including a large number of parallel belt cords and a band including a spirally wound band cord, the belt comprises an inner belt ply and an outer belt ply arranged in a radial direction; the direction of inclination of the belt cords included in the inner belt ply is opposite to the direction of inclination of the belt cords included in the outer belt ply, The band includes a full band formed by spirally winding a full band strip, the full band is located between the inner belt ply and the outer belt ply, The full band strip is a cord arrangement in which a plurality of the band cords are arranged, The number of the band cords included in the full band strip is 2 or more and 5 or less. Heavy duty tires.

2. The number of the band cords included in the full band strip is three.

2. The heavy duty tire according to claim 1.

3. The band further comprises a pair of edge bands formed by spirally wrapping an edge band strip; The edge band strip is a cord arrangement in which a plurality of the band cords are arranged, The pair of edge bands are each located radially outward of the end of the full band.

2. The heavy duty tire according to claim 1.

4. The number of the band cords included in the edge band strip is 2 or more and 5 or less.

4. The heavy duty tire according to claim 3.

5. the tread includes a base portion located radially outward of the reinforcing layer, and a cap portion located radially outward of the base portion and having the tread surface, a ratio of a thickness of the base portion to a thickness of the tire on a normal line of the carcass that passes through an edge of the tread surface is 1 / 3 or less; The heavy duty tire according to any one of claims 1 to 4.

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