tire

Abstract

To provide a tire 2 which can achieve improvement of durability without causing increase of rolling resistance.SOLUTION: A tire 2 includes a bead 8, a carcass 10, a side wall layer 6, a tread 4, a belt 12, and a band 14. A carcass ply 42 of the carcass 10 includes a ply body 44 and a pair of folded parts 46. An end PF of the folded part 46 is located at the axial inner side of an end PE of the belt 12. A ratio D / E, which is a ratio of a thickness D from the carcass 10 to an outer surface 2G of the tire 2 along a first normal line LD to a thickness E from the carcass 10 to the outer surface 2G of the tire 2 along a second normal line LW, is not less than 1 and not more than 2.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to tires, and more particularly to tires mounted on passenger vehicles. [Background technology]

[0002] Tire mass affects rolling resistance, and environmental considerations mean there is a demand for tires with low rolling resistance. In order to reduce the weight of the tire, if the number of carcass plies constituting the carcass is reduced, or the length of the turned-up portion of the carcass ply is shortened, the rigidity of the tire will decrease. Loads act on tires. Tires undergo repeated deformation and recovery while in motion. Tire rigidity affects durability. Reinforcing tires by incorporating new elements to improve durability increases the tire's mass. Therefore, various studies have been conducted to establish a technology that can improve durability while reducing the weight of tires (for example, Patent Document 1 below). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 9-286211 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a tire that can achieve improved durability without increasing rolling resistance. [Means for solving the problem]

[0005] A tire according to the present invention has a load index LI that satisfies the relationship shown in the following formula (1) or (2). The tire includes a pair of beads, a carcass spanning the pair of beads, a pair of sidewall layers located axially outward of the carcass, a tread located radially outward of the carcass and in contact with the road surface, a belt including a number of parallel belt cords, and a band including a spirally wound band cord. The belt is laminated on the carcass radially inward of the tread. The band is located radially between the tread and the belt. The carcass is formed of a single carcass ply including a number of parallel carcass cords. The carcass ply includes a ply body and a pair of turn-up portions. The ply body spans the pair of beads. Each of the turn-up portions is continuous with the ply body and is turned up from the axially inner side to the axially outer side at each of the beads. Ends of the turn-up portions are located axially inward of the ends of the belt. A normal line to the carcass that passes through the intersection of a first imaginary line that passes through the end of the belt and extends axially with the outer surface of the tire is a first normal line. A normal line to the carcass that passes through the maximum width position of the tire is a second normal line. A ratio D / E of a thickness D from the carcass to the outer surface of the tire along the first normal line to a thickness E from the carcass to the outer surface of the tire along the second normal line is 1 or greater and 2 or less. Formula (1): LIx≦LI≦LIx+4 Equation (2): LI = LIh LIx in the formula (1) and LIh in the formula (2) are as follows: LIx: The load index of an EXTRA LOAD CAPACITY type tire specified in the ETRTO 2019 standard manual, which has the same dimensional and structural characteristics as the dimensional and structural characteristics included in the tire designation of the tire. LIh: The load index of a HIGH LOAD CAPACITY type tire specified in the ETRTO 2021 standard manual, which has the same dimensional and structural characteristics as the dimensional and structural characteristics included in the tire designation of the tire. [Effects of the Invention]

[0006] According to the present invention, a tire can be obtained that can achieve improved durability without increasing rolling resistance. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a cross-sectional view showing a portion of a tire according to one embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view taken along the equatorial plane of FIG. [Figure 3] FIG. 2 is an enlarged cross-sectional view showing a part of the cross section of FIG. [Figure 4] FIG. 2 is a schematic diagram illustrating the configuration of a belt. [Figure 5] FIG. 4 is a cross-sectional view taken along line LD in FIG. [Figure 6] FIG. 4 is a cross-sectional view taken along line LW in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, the present invention will be described in detail based on preferred embodiments, with appropriate reference to the drawings.

[0009] 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.

[0010] 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 the standard internal pressure, and no load is applied to the tire is called the standard state. The state in which a tire is mounted on a standard rim, the internal pressure of the tire is adjusted to 290 kPa, and no load is applied to the tire is called the reference state.

[0011] 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.

[0012] 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.

[0013] 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.

[0014] 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.

[0015] In the present invention, unless otherwise specified, the load index (LI) is defined in the JATMA standard and is an index that represents the maximum mass that can be loaded onto a tire under specified conditions, i.e., the maximum load capacity.

[0016] In the present invention, the "dimensional and structural characteristics included in the tire nominal designation" refers to the dimensional and structural characteristics expressed as "nominal section width," "nominal aspect ratio," "tire structure symbol," and "nominal rim diameter" included in the "tire nominal designation" defined in JIS D4202 "Automobile tires - Designation and specifications." The dimensional and structural characteristics are also called tire size. In the present invention, the terms "nominal cross-sectional width" and "nominal aspect ratio" refer to the "nominal cross-sectional width" and "nominal aspect ratio" included in the dimensional structural characteristics. For example, if the "tire designation" is "195 / 65R16 106 / 104 L LT," the "195 / 65R16" included in this "tire designation" is the dimensional structural characteristic, "195" is the nominal cross-sectional width, and "65" is the nominal aspect ratio.

[0017] 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 boundary between the tread and the sidewall is also called a buttress.

[0018] [Findings that form the basis of the present invention] Electric vehicles are becoming more popular due to environmental concerns. Electric vehicles are equipped with batteries. Batteries that allow a vehicle to travel around 500 km are heavy. Electric vehicles tend to be heavier than conventional gasoline-powered vehicles. As a result, tires mounted on electric vehicles are subjected to higher loads than tires mounted on gasoline-powered vehicles. In order to provide tires that can support high loads, the load index has been revised in the ETRTO standard, and high load capacity type (hereinafter referred to as HLC type) tires have been introduced as a new category. To be used as an HLC type tire, the tire must be able to support a higher load than conventional tires. To achieve this, the rigidity of the tire must be increased, but as mentioned above, there is a concern that increasing the rigidity of the tire will increase the mass of the tire. Since an increase in the mass of a tire leads to an increase in rolling resistance, the inventor discovered that by reviewing the carcass structure and the thickness of each part of the tire, it is possible to impart the necessary rigidity to a tire even if the carcass is constructed with one carcass ply instead of two, and this led to the completion of the invention described below.

[0019] [Outline of the embodiment of the present invention] The present invention provides a tire having a load index LI that satisfies the relationship shown in the following formula (1) or (2), the tire comprising: a pair of beads; a carcass spanning the pair of beads; a pair of sidewall layers located axially outward of the carcass; a tread located radially outward of the carcass and in contact with a road surface; a belt including a large number of belt cords arranged in parallel; and a band including a spirally wound band cord, wherein the belt is laminated on the carcass radially inward of the tread, the band is located radially between the tread and the belt, the carcass is composed of a single carcass ply including a large number of carcass cords arranged in parallel, and the carcass ply is a ply. a) a tire comprising a main body and a pair of turned-up portions, the ply main body spanning between the pair of beads, each of the turned-up portions being continuous with the ply main body and turned up from the axially inner side to the axially outer side at each of the beads, an end of the turned-up portion being located axially inner side of the end of the belt, a first normal line passing through the end of the belt and passing through an intersection of a first imaginary line extending axially with the outer surface of the tire, the first normal line being a normal to the carcass and passing through a maximum width position of the tire, and a second normal line being a normal to the carcass, and a ratio D / E of a thickness D from the carcass to the outer surface of the tire along the first normal line to a thickness E from the carcass to the outer surface of the tire along the second normal line is 1 or more and 2 or less. Formula (1): LIx≦LI≦LIx+4 Equation (2): LI = LIh LIx in the formula (1) and LIh in the formula (2) are as follows: LIx: The load index of an EXTRA LOAD CAPACITY type tire specified in the ETRTO 2019 standard manual, which has the same dimensional and structural characteristics as the dimensional and structural characteristics included in the tire designation of the tire. LIh: The load index of a HIGH LOAD CAPACITY type tire specified in the ETRTO 2021 standard manual, which has the same dimensional and structural characteristics as the dimensional and structural characteristics included in the tire designation of the tire.

[0020] The tire of the present invention can achieve improved durability without increasing rolling resistance. The mechanism by which this effect is achieved has not been clarified, but is presumed to be as follows.

[0021] The thickness of the outer carcass portion, expressed as the distance from the carcass to the outer surface of the tire along a line normal to the carcass, affects rolling resistance and durability. The part where the first normal intersects with the outer surface of the tire, i.e., the carcass outer part at the buttress, affects the rolling resistance. If the thickness D of the carcass outer part along the first normal is large, the rolling resistance increases. The outer carcass portion where the second normal intersects with the tire's outer surface, i.e., where the tire is at its widest point, affects durability. If the thickness E of the outer carcass portion along the second normal is small, durability decreases, especially when a high load is applied. In this tire, a ratio D / E of a thickness D of the carcass outer portion along the first normal line to a thickness E of the carcass outer portion along the second normal line is equal to or greater than 1 and equal to or less than 2. In this tire, the effect of the carcass outer portion at the buttress on rolling resistance can be suppressed, and the effect of the carcass outer portion at the maximum width position on durability can be suppressed. This tire can achieve improved durability without increasing rolling resistance.

[0022] When a tire is expected to be subjected to a high load, increasing the recommended air pressure is considered. In this case, the tire is reinforced, increasing its rigidity. However, such reinforcement results in an increase in mass. From the perspective of reducing rolling resistance, a tire is required to withstand the action of a high load without increasing the recommended air pressure. Therefore, the inventors focused on the carcass, which forms the skeleton of the tire, and studied the ratio of the carcass thickness to the tire thickness. They found that if the ratio of the carcass thickness to the tire thickness is too low, the tire cannot withstand the action of a high load, and conversely, if the ratio of the carcass thickness to the tire thickness is too high, there will be insufficient rubber, resulting in reduced wear resistance. Based on this finding, in this tire, preferably, the ratio TCa / TA of the carcass thickness TCa at the tire's equatorial plane to the tire's thickness TA at the tire's equatorial plane is 0.03 or more and 0.1 or less, the ratio TCh / T1 of the carcass thickness TCh along the first normal line to the tire's thickness T1 along the first normal line is 0.05 or more and 0.35 or less, and the ratio TCe / T2 of the carcass thickness TCe along the second normal line to the tire's thickness T2 along the second normal line is 0.06 or more and 0.55 or less. In this case, the proportion of the carcass thickness in the tire thickness at each tire portion is adjusted. The carcass can adequately withstand the action of high loads, contributing to maintaining good wear resistance. This tire can achieve improved durability.

[0023] Preferably, the difference between the ratio TCe / T2 and the ratio TCh / T1 (TCe / T2-TCh / T1) is equal to or greater than 0.0 and equal to or less than 0.5. In this case, the tire can achieve further improvement in durability.

[0024] Preferably, the outer diameter of the carcass cord is 0.6 mm or more and 0.8 mm or less, in which case the tire can have improved durability without increasing rolling resistance.

[0025] The inventors further confirmed the ratio of the belt width to the tire section width and the thickness of the sidewall layer at the bead portion, and found that the two are correlated, and that as long as the belt width is within an appropriate range relative to the tire section width, the tire can be provided with the required rigidity even if the carcass is constructed with one carcass ply instead of two. Based on this finding, in this tire, preferably, the average thickness F of the sidewall layer in a zone radially distanced from the bead base line of 20 mm to 30 mm satisfies the following formula (3) expressed using a constant B and the tire section width SW and belt width BW obtained in a reference state in which the tire is mounted on a regular rim, the internal pressure of the tire is adjusted to 290 kPa, and no load is applied to the tire, and the constant B satisfies the following formula (4) expressed using the aspect ratio RA of the tire: Formula (3): 380×(BW / SW-B) 2 +3.5≦F≦380×(BW / SW-B) 2 +5.5 Equation (4): B=0.84×(-0.49×RA / 100+1.22)

[0026] As a tire rolls, the surface of the zone ZF undergoes repeated compressive deformation. Because the carcass is susceptible to compressive deformation, a common measure is to thicken the sidewall layer in the zone ZF and move the carcass away from the tire surface to reduce the impact of compressive deformation on the carcass. However, this approach not only makes it difficult to reduce the tire's weight, but also raises concerns that it promotes heat accumulation, reducing durability. For this reason, the thickness of the sidewall layer in the zone ZF in conventional tires is set within the range of 6 to 12 mm. In contrast, in the tire of the present invention, the average thickness F of the sidewall layer in zone ZF satisfies the above-mentioned formula (3), thereby achieving a good balance between the belt width BW and the thickness of the sidewall layer in zone ZF. The average thickness F of the sidewall layer is set to match the belt width BW. In other words, this tire can optimize the average thickness F while reducing compressive strain generated in the carcass. Since the average thickness F is set to a required thickness, the tire can be made lighter. Since compressive strain generated in the carcass is reduced, this tire can fully withstand the action of the load represented by the load index expressed by the above-mentioned formula (1) or (2) even when the load is applied. In particular, by setting the ratio of the belt width BW to the tire's cross-sectional width SW (BW / SW) to be equal to the constant B expressed by formula (4), tire 2 can exhibit good durability even when the average thickness F of the sidewall layer in zone ZF is set to 3.5 to 5.5 mm. Even if the carcass of this tire is made up of one carcass ply instead of two, the sidewall layer in the bead portion can be effectively thinned while maintaining the rigidity required for the tire. This tire can achieve improved durability without increasing rolling resistance.

[0027] In this way, the tire of the present invention can achieve improved durability without increasing rolling resistance, which will be explained in detail below using the tire shown in FIG.

[0028] [Details of the embodiment of the present invention]

[0029] 1 shows a portion of a tire 2 according to one embodiment of the present invention. The tire 2 is a pneumatic tire for passenger cars. The load index LI of the tire 2 of the present invention satisfies the relationship shown in the following formula (1) or formula (2). Formula (1): LIx≦LI≦LIx+4 Equation (2): LI = LIh

[0030] LIx in formula (1) and LIh in formula (2) are as follows: LIx: Load index of an EXTRA LOAD CAPACITY type tire specified in the ETRTO 2019 standard manual that has the same dimensional and structural characteristics as those included in the tire designation of tire 2. LIh: Load index of a HIGH LOAD CAPACITY type tire specified in the ETRTO 2021 standard manual that has the same dimensional and structural characteristics as those included in the tire designation of tire 2

[0031] The tire 2 shown in Fig. 1 is a HIGH LOAD CAPACITY type tire defined in the ETRTO 2021 standard manual. The load index LI of this tire 2 satisfies the relationship shown in the above-mentioned formula (2).

[0032] Fig. 1 shows a portion of a cross section of a tire 2 taken along a plane including the rotation axis (not shown) of the tire 2. The cross section shown in Fig. 1 is also called a meridian cross section. The tire 2 shown in Fig. 1 is a brand new tire with no running history.

[0033] 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 the 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 the paper in 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. The direction approaching the equatorial plane in the axial direction is the inner side of the tire 2, and the direction moving away from the equatorial plane is the outer side of the tire 2 in the axial direction. 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.

[0034] FIG. 1 shows a tire 2 mounted on a rim R. For example, air is filled between the tire 2 and the rim R, and the air pressure inside the tire 2 (i.e., the internal pressure of the tire 2) is adjusted. The rim R is a regular rim. More specifically, this rim R is a "standard rim" in the JATMA standard. The state of the tire 2 shown in FIG. 1 is the reference state described above.

[0035] In Fig. 1, the solid line BBL extending in the axial direction is the bead base line, which is a line that defines the rim diameter of the rim R (see JATMA, etc.).

[0036] 1, the position indicated by the symbol Eq is the intersection point between the outer surface 2G of the tire 2 (specifically, the tread surface described later) and the equatorial plane. When a groove is located on the equatorial plane, the equator Eq is determined based on a virtual outer surface obtained assuming that there is no groove. The equator Eq is the radially outer edge of the tire 2. The equator Eq of the tire 2 is determined with the tire 2 in a reference state. The length indicated by the double-headed arrow SH in FIG. 1, that is, the radial distance from the bead base line to the equator Eq of the tire 2, is the cross-sectional height of the tire 2.

[0037] In the present invention, the section height SH of the tire 2 is expressed as the product of the nominal section width and the nominal aspect ratio. For example, if the tire size of the tire 2 is 245 / 45R18, the nominal section width of the tire 2 is 245 mm and the nominal aspect ratio is 45%. In this case, the section height SH of the tire 2 is 110.25 mm.

[0038] 1, the position indicated by the symbol PW is the axial outer end (hereinafter referred to as the outer end PW) of the tire 2. If there is a decoration such as a pattern or lettering on the outer surface, the outer end PW is identified based on a virtual outer surface obtained assuming that there is no decoration. The length indicated by the double-headed arrow SW in FIG. 1 is the section width of the tire 2. The section width SW is expressed as the axial distance from the first outer end PW to the second outer end PW. The section width SW is also the maximum width of the tire 2. The outer end PW is the position indicating the maximum width SW, and is also referred to as the maximum width position PW. This section width SW of the tire 2 is determined for the tire 2 in a reference state.

[0039] The tire 2 includes a tread 4 , a pair of sidewall layers 6 , a pair of beads 8 , a carcass 10 , a belt 12 , a band 14 , a pair of chafers 16 , and an inner liner 18 .

[0040] The tread 4 is located radially outward of the carcass 10. The tread 4 is made of crosslinked rubber. The tread 4 comes into contact with the road surface at a tread surface 22. The tread 4 has the tread surface 22. The outer surface 2G of the tire 2 includes the tread surface 22. Grooves 24 are cut into the tread 4, thereby forming a tread pattern.

[0041] The tread 4 has a tread body 26 and a pair of wings 28 . Each wing 28 is positioned between the tread body 26 and the sidewall layer 6. The tread body 26 and the sidewall layer 6 are joined via the wing 28. The wing 28 is made of crosslinked rubber in consideration of adhesiveness. The tread body 26 includes a cap portion 30 and a base portion 32 . The cap portion 30 includes the tread surface 22. The cap portion 30 comes into contact with the road surface. The cap portion 30 is made of crosslinked rubber that takes into consideration wear resistance and grip performance. The base portion 32 is located radially inside the cap portion 30. The base portion 32 is covered by the cap portion 30. The base portion 32 is made of a cross-linked rubber with low heat buildup.

[0042] Each sidewall layer 6 is continuous with the tread 4. The sidewall layer 6 is located radially inward of the tread 4. The sidewall layer 6 is located axially outward of the carcass 10. The sidewall layer 6 includes a sidewall body 34 and a clinch 36. The sidewall main body 34 is continuous with the tread 4. The sidewall main body 34 is made of crosslinked rubber in consideration of cut resistance. The clinch 36 is located radially inside the sidewall body 34. The clinch 36 contacts the rim R. The clinch 36 is located axially outside the bead 8. The clinch 36 is made of crosslinked rubber in consideration of wear resistance.

[0043] Each bead 8 is located radially inward of the sidewall layer 6. Specifically, the bead 8 is located radially inward of the sidewall body 34 and axially inward of the clinch 36. The bead 8 includes a core 38 and an apex 40. The core 38 extends in the circumferential direction. Although not shown, the core 38 includes a steel wire. The apex 40 is located radially outward of the core 38. The apex 40 is made of cross-linked rubber with high rigidity. The apex 40 tapers radially outward. The position indicated by the symbol PA is the outer end of the apex 40. The outer end PA of the apex 40 is the outer end of the bead 8. When one bead 8 of a pair of beads 8 is called a first bead 8, the other bead 8 is called a second bead 8.

[0044] The carcass 10 is located inside the tread 4 and the pair of sidewall layers 6. The carcass 10 bridges between the pair of beads 8. The carcass 10 bridges between the first bead 8 and the second bead 8.

[0045] The carcass 10 is composed of one carcass ply 42. The carcass 10 of the tire 2 is lighter than a carcass including two or more carcass plies 42. The carcass ply 42 is turned up from the inside to the outside in the axial direction at each bead 8. The carcass ply 42 includes a ply body 44 and a pair of turned-up portions 46. The ply body 44 spans between the pair of beads 8. Each turned-up portion 46 is continuous with the ply body 44 and is turned up at each bead 8. As described above, the carcass 10 of the tire 2 is configured with one carcass ply 42. Therefore, the number of carcass plies 42 located radially inward of the bead 8 is one.

[0046] 2 is a cross section of the tire 2 taken along the equatorial plane. The direction indicated by the arrow CD is the circumferential direction of the tire 2.

[0047] As shown in Fig. 2, the carcass ply 42 includes a large number of carcass cords 48 arranged in parallel. These carcass cords 48 are covered with a carcass topping rubber 50. The carcass cords 48 intersect with the equator plane. The carcass cords 48 bridge between the first bead 8 and the second bead 8. The carcass 10 of the tire 2 has a radial structure. The carcass cords 48 of the tire 2 are cords made of organic fibers (hereinafter referred to as organic fiber cords). Examples of organic fibers include nylon fibers, rayon fibers, polyester fibers, and aramid fibers.

[0048] Although not shown, the carcass cord 48 is formed by twisting together a plurality of filaments made of organic fibers. The number of filaments constituting the carcass cord 48 is usually two. However, the number may be three or four. The outer diameter of the filaments before twisting is preferably 0.6 mm or more and 0.8 mm or less.

[0049] Fig. 3 shows a part of the cross section of Fig. 1. Fig. 3 shows a sidewall portion of a tire 2. An end PF of a turned-up portion 46 of this tire 2 is located radially outward from the maximum width position PW. The position indicated by the symbol PE is the end of the belt 12. The end PF of the turned-up portion 46 is located axially inward from the end PE of the belt 12. An end PF of the turned-up portion 46 is sandwiched between the carcass 10 and the belt 12. The turned-up portion 46 overlaps with an end PE of the belt 12. The carcass 10 of the tire 2 has an ultra-high turn-up (U-HTU) structure. As described above, the carcass 10 of the tire 2 is composed of one carcass ply 42. The structure of the carcass 10 is represented as "1-0UHTU."

[0050] In the carcass 10, the portion between the end PF of one turned-up portion 46 and the end PF of the other turned-up portion 46 is made up of the ply body 44. This portion appears to be made up of one carcass ply 42. The portion between the end PF of the turned-up portion 46 and the outer end PA of the bead 8 is made up of the ply body 44 and the turned-up portion 46. This portion appears to be made up of two carcass plies 42 stacked together. In the radially inner portion of the outer end PA of the bead 8, the carcass ply 42 forms a loop. The number of carcass plies 42 that form the loop is one. The bead 8 is housed in the loop. The loop surrounds the bead 8.

[0051] The belt 12 is located on the radially inner side of the tread 4. The belt 12 is located on the radially outer side of the carcass 10. The belt 12 of this tire 2 is laminated on the carcass 10 on the radially inner side of the tread 4. 1, the length indicated by the double-headed arrow BW is the width of the belt 12. The width BW of the belt 12 is represented by the axial distance from one end PE of the belt 12 to the other end PE. In the tire 2, the ratio BW / SW of the width BW of the belt 12 to the cross-sectional width SW of the tire 2 is 0.65 or greater and 1.00 or less. The ratio BW / SW is preferably 0.70 or greater and 0.95 or less.

[0052] The belt 12 includes a plurality of belt plies 52 arranged in the radial direction. The plurality of belt plies 52 includes an inner belt ply 54 located at the innermost side and an outer belt ply 56 located at the outermost side. The belt 12 of the tire 2 is composed of two belt plies 52. In detail, the belt 12 is composed of the inner belt ply 54 and the outer belt ply 56. The inner belt ply 54 is laminated to the carcass 10 radially inside of the tread 4. The outer belt ply 56 is laminated to the inner belt ply 54.

[0053] The end of the outer belt ply 56 is located axially inward of the end of the inner belt ply 54. The outer belt ply 56 is narrower than the inner belt ply 54. The length from the end of the outer belt ply 56 to the end of the inner belt ply 54 is 3 mm or more and 10 mm or less. The width BW of the belt 12 described above is represented by the width of the wider inner belt ply 54. The end of the inner belt ply 54 is the end PE of the belt 12.

[0054] 4 shows the configuration of the belt 12. The direction indicated by the double arrow AD is the axial direction of the tire 2. The direction indicated by the double arrow CD is the circumferential direction of the tire 2. The front side of the paper is the radially outer side, and the back side is the radially inner side.

[0055] Each of the plurality of belt plies 52 constituting the belt 12 includes a large number of parallel belt cords 58. The belt cords 58 are steel cords. For ease of explanation, the belt cords 58 are represented by solid lines, but the belt cords 58 are covered with a topping rubber 60. Each belt cord 58 is inclined with respect to the equator plane. The inclination direction of the belt cord 58 included in the outer belt ply 56 (hereinafter referred to as the outer belt cord 58s) is opposite to the inclination direction of the belt cord 58 included in the inner belt ply 54 (hereinafter referred to as the inner belt cord 58u).

[0056] The angle indicated by the symbol θb is the angle that the belt cord 58 included in the belt 12 makes with respect to the equator plane (hereinafter referred to as the inclination angle of the belt cord 58).

[0057] From the viewpoint of enabling the belt 12 to effectively contribute to suppressing distortion of the contour of the carcass 10, in the standard state, the inclination angle θb of the belt cords 58 is preferably 20 degrees or more and 32 degrees or less, and more preferably 24 degrees or more and 30 degrees or less. In this case, it is more preferable that the inclination angle θb of the belt cords 58 included in the inner belt ply 54 and the inclination angle θb of the belt cords 58 included in the outer belt ply 56 are the same.

[0058] The band 14 is laminated on the belt 12 on the inside of the tread 4. The band 14 is located between the tread 4 and the belt 12 in the radial direction. The position indicated by the symbol PB is the end of the band 14. The end PB of the band 14 is located axially outward of the end PE of the belt 12. The length from the end PE of the belt 12 to the end PB of the band 14 is 3 mm or more and 7 mm or less.

[0059] The band 14 of this tire 2 includes a full band 62. The band 14 is configured with the full band 62. The full band 62 covers the entire belt 12 from the radially outer side. The band 14 may further include a pair of edge bands. In this case, the pair of edge bands are arranged spaced apart in the axial direction across the equatorial plane, and each edge band covers the end of the full band 62 from the radially outer side. The band 14 may be composed of only a pair of edge bands. In this case, the pair of edge bands are arranged spaced apart in the axial direction across the equatorial plane, and each edge band covers the end PE of the belt 12 from the radially outer side.

[0060] Although not shown, the full band 62 constituting the band 14 includes a spirally wound band cord. In the band 14, the band cord extends substantially in the circumferential direction. Specifically, the angle that the band cord makes with the circumferential direction is 5° or less. The band 14 has a jointless structure. The band cord of the tire 2 is an organic fiber cord. Examples of the organic fiber include nylon fiber, rayon fiber, polyester fiber, and aramid fiber.

[0061] Each chafer 16 is located radially inward of the bead 8. The chafers 16 contact the rim R. In the tire 2, the chafers 16 are made of a cloth and rubber impregnated into the cloth. The inner end of the chafer 16 forms a part of the inner surface 2N of the tire 2. The outer end of the chafer 16 is located radially outward of the inner end. The outer end of the chafer 16 is located between the bead 8 and the clinch 36.

[0062] The inner liner 18 is located inside the carcass 10. The inner liner 18 constitutes the inner surface 2N of the tire 2. The inner liner 18 is made of crosslinked rubber that has excellent air barrier properties. The inner liner 18 maintains the internal pressure of the tire 2.

[0063] 3, a solid line LE is a straight line extending in the axial direction and passing through the end PE of the belt 12. In the present invention, the solid line LE is called a first imaginary line. The position indicated by the symbol PD is the intersection point between the first imaginary line LE and the outer surface 2G of the tire 2. The solid line LD is a normal line to the carcass 10 that passes through the intersection point PD. In the present invention, the solid line LD is called the first normal line to the carcass 10. The solid line LW is a normal line to the carcass 10 that passes through the maximum width position PW. In the present invention, the solid line LW is called the second normal line to the carcass 10.

[0064] As described above, the carcass 10 is composed of one carcass ply 42, and the carcass ply 42 includes the carcass cords 48. Since the carcass 10 has a radial structure, the carcass cords 48 span between one end and the other end of the carcass ply 42. The shape of the carcass ply 42 in a meridian cross section is represented by the center lines of the carcass cords 48. The shape of the carcass ply 48 represented by the center lines of the carcass cords 48 is also called the carcass line. In the present invention, the normal to the carcass 10 is represented by the normal to the carcass line. When the carcass line overlaps twice, such as in the portion where the turned-up portion 46 is layered on the ply body 44, the normal to the carcass 10 is determined based on the carcass line on the outer surface side of the tire 2.

[0065] Fig. 5 shows a part of the cross section of the tire 2 along the first normal line LD of the carcass 10 shown in Fig. 3. The up-down direction coincides with the direction of the first normal line LD. The length indicated by the double arrow D is the thickness from the carcass 10 to the outer surface 2G of the tire 2 along the first normal LD, i.e., the thickness of the rubber component located on the outside of the carcass 10. The thickness D is also called the thickness of the outer part of the carcass 10 at the buttress. The first normal LD ​​crosses, from the inside, the inner liner 18, the carcass 10, the tread 4, and the sidewall layer 6. This thickness D is equal to the sum of the thickness of the tread 4 and the thickness of the sidewall layer 6, measured along the first normal LD.

[0066] Fig. 6 shows a part of the cross section of the tire 2 along the second normal line LW of the carcass 10 shown in Fig. 3. The up-down direction coincides with the direction of the second normal line LW. The length indicated by the double arrow E is the thickness from the carcass 10 to the outer surface 2G of the tire 2 along the second normal line LW. The thickness E is also referred to as the thickness of the outer portion of the carcass 10 at the maximum width position PW. The second normal line LW intersects the inner liner 18, the carcass 10, and the sidewall layer 6 from the inside. This thickness E is equal to the thickness of the sidewall layer 6 measured along the second normal line LW.

[0067] A ratio D / E of a thickness D of the outer portion of the carcass 10 along the first normal line LD to a thickness E of the outer portion of the carcass 10 along the second normal line LW is 1 or more and 2 or less. Since the ratio D / E is 1 or greater, the tire 2 can ensure the rigidity required particularly in the buttress. And since the ratio D / E is 2 or less, the tire 2 can suppress the effect on rolling resistance of the outer portion of the carcass 10 at the buttress, and can suppress the effect on durability of the outer portion of the carcass 10 at the maximum width position. From this viewpoint, the ratio D / E is preferably 1.0 or greater and 1.5 or less. This tire 2 can suppress the influence on rolling resistance of the outer portion of the carcass 10 at the buttress while ensuring necessary rigidity, and can also suppress the influence on durability of the outer portion of the carcass 10 at the maximum width position. The tire 2 can achieve improved durability without increasing rolling resistance.

[0068] 2, the length indicated by the double arrow A is the thickness of the tread 4 on the equatorial plane. The thickness A is expressed as the thickness of the tread 4 along the equatorial plane in a meridian cross section. From the viewpoint of ensuring the necessary rigidity of the tread 4, the ratio D / A of the thickness D of the outer portion of the carcass 10 at the buttress to the thickness A of the tread 4 at the equatorial plane is preferably 0.3 or more, and more preferably 0.5 or more. From the viewpoint of reducing rolling resistance, the ratio D / A is preferably 1.2 or less, and more preferably 0.8 or less. From the viewpoint of ensuring rigidity and reducing rolling resistance, the thickness A of the tread 4 at the equatorial plane is preferably 8.0 mm or greater and 13.0 mm or less.

[0069] In Fig. 2, the double-headed arrow TA indicates the thickness of the tire 2 on the equatorial plane. The thickness TA is expressed as the thickness from the inner surface 2N to the outer surface 2G of the tire 2 along the equatorial plane in the meridian cross section. The length indicated by the double-headed arrow TCa is the thickness of the carcass 10 on the equatorial plane. The thickness TCa is expressed as the thickness of the carcass 10 along the equatorial plane in the meridian cross section. As described above, the portion between the end PF of one turned-up portion 46 and the end PF of the other turned-up portion 46 is formed only by the ply body 44. The thickness TCa corresponds to the thickness of one carcass ply 42.

[0070] 5, the double-headed arrow T1 indicates the thickness of the tire 2 along the first normal line LD. The thickness T1 is expressed as the thickness from the inner surface 2N to the outer surface 2G of the tire 2 along the first normal line LD. The length indicated by the double-headed arrow TCh is the thickness of the carcass 10 along the first normal line LD. As described above, the portion between the end PF of the turned-up portion 46 and the outer end PA of the bead 8 is composed of the ply body 44 and the turned-up portion 46. This thickness TCh corresponds to the thickness of two carcass plies 42.

[0071] 6, the double-headed arrow T2 indicates the thickness of the tire 2 along the second normal line LW. The thickness T2 is expressed as the thickness from the inner surface 2N to the outer surface 2G of the tire 2 along the second normal line LW. The length indicated by the double-headed arrow TCe is the thickness of the carcass 10 along the second normal line LW. As described above, the portion between the end PF of the turned-up portion 46 and the outer end PA of the bead 8 is composed of the ply body 44 and the turned-up portion 46. Like the thickness TCh described above, this thickness TCe also corresponds to the thickness of two carcass plies 42.

[0072] As mentioned above, if a tire is expected to be subjected to a high load, it is considered to increase the recommended air pressure. In this case, the tire is reinforced and its rigidity is increased. However, such reinforcement results in an increase in mass. From the perspective of reducing rolling resistance, the tire is required to withstand the action of a high load without increasing the recommended air pressure. Therefore, as described above, the inventors focused on the carcass that forms the framework of the tire and studied the ratio of the carcass thickness to the tire thickness.

[0073] The ratio TCa / TA of the thickness TCa of the carcass 10 at the equatorial plane to the thickness TA of the tire 2 at the equatorial plane is preferably 0.03 or greater and 0.1 or less. By setting the ratio TCa / TA to 0.03 or more, the carcass 10 at the equatorial plane can effectively reinforce the tire 2. The rigidity of the tire 2 is increased. Even if a high load acts on the tire 2, the tire 2 can withstand the action of the high load. Since the amount of rubber is maintained appropriately, an increase in rolling resistance is suppressed. From this viewpoint, it is more preferable that the ratio is 0.05 or more. By setting the ratio TCa / TA to 0.1 or less, the tire 2 can ensure a sufficient amount of rubber in the outer portion of the carcass 10. This tire 2 can maintain good wear resistance. From this viewpoint, it is more preferable that the ratio be 0.08 or less.

[0074] The ratio TCh / T1 of the thickness TCh of the carcass 10 along the first normal line LD to the thickness T1 of the tire 2 along the first normal line LD is preferably 0.05 or greater and 0.35 or less. By setting the ratio TCh / T1 to 0.05 or more, the carcass 10 can effectively reinforce the tire 2 at the buttress. The rigidity of the tire 2 is increased. Even if a high load acts on the tire 2, the tire 2 can withstand the action of the high load. Since the amount of rubber is maintained appropriately, an increase in rolling resistance is suppressed. From this viewpoint, it is more preferable that the ratio is 0.15 or more, and even more preferable that it is 0.20 or more. By setting the ratio TCh / T1 to 0.35 or less, the tire 2 can ensure a sufficient amount of rubber in the outer portion of the carcass 10. The tire 2 can maintain good wear resistance. The outer portion of the carcass 10 can deform in accordance with the deformation of the tire 2. The tire 2 can maintain good durability. From this viewpoint, it is more preferable that the ratio is 0.30 or less, and even more preferable that it is 0.25 or less.

[0075] The ratio TCe / T2 of the thickness TCe of the carcass 10 along the second normal line LW to the thickness T2 of the tire 2 along the second normal line LW is preferably 0.06 or greater and 0.55 or less. By setting the ratio TCe / T2 to 0.06 or more, the carcass 10 can effectively reinforce the tire 2 at the maximum width position PW. The rigidity of the tire 2 is increased. Even if a high load acts on the tire 2, the tire 2 can withstand the action of the high load. Since the amount of rubber is maintained appropriately, an increase in rolling resistance is suppressed. From this viewpoint, it is more preferable that the ratio is 0.15 or more, and even more preferable that it is 0.20 or more. By setting the ratio TCe / T2 to 0.55 or less, the tire 2 can ensure a sufficient amount of rubber in the outer portion of the carcass 10. The outer portion of the carcass 10 can deform in accordance with the deformation of the tire 2. The tire 2 can maintain good durability. From this viewpoint, it is more preferable that the ratio is 0.40 or less, and even more preferable that the ratio is 0.30 or less.

[0076] From the viewpoint of enabling the carcass 10 to effectively contribute to the tire 2 withstanding the action of a high load, it is more preferable that the ratio TCa / TA of the thickness TCa of the carcass 10 at the equatorial plane to the thickness TA of the tire 2 at the equatorial plane is 0.03 or more and 0.1 or less, the ratio TCh / T1 of the thickness TCh of the carcass 10 along the first normal line LD to the thickness T1 of the tire 2 along the first normal line LD is 0.05 or more and 0.35 or less, and the ratio TCe / T2 of the thickness TCe of the carcass 10 along the second normal line LW to the thickness T2 of the tire 2 along the second normal line LW is 0.06 or more and 0.55 or less. In this case, the tire 2 can effectively withstand the action of a high load without increasing the recommended air pressure. The tire 2 can achieve improved durability without increasing rolling resistance. From this viewpoint, the difference between the ratio TCe / T2 and the ratio TCh / T1 is preferably 0.0 or more and 0.5 or less, and more preferably 0.00 or more and 0.10 or less.

[0077] 3, the position indicated by the symbol FN is a position on the outer surface 2G of the tire 2. The radial distance HN from the bead base line to the position FN is 20 mm. The position indicated by the symbol FG is a position on the outer surface 2G of the tire 2. The radial distance HG from the bead base line to the position FG is 30 mm. In Fig. 3, the zone from position FN to position FG is represented as zone ZF, which is a zone whose radial distance from the bead base line is 20 mm to 30 mm. Position FN is the inner edge of zone ZF, and position FG is the outer edge of zone ZF. The position indicated by the symbol FC is the intersection point between the radial center line of the zone ZF and the outer surface 2G of the tire 2. The position FC is the center of the zone ZF.

[0078] The action of the load causes strain in the tire 2. In particular, large compressive strain occurs near the zone ZF. To prevent damage to the bead portion, the sidewall layer 6 is configured so that the area near the zone ZF is thicker than other areas.

[0079] 3, the length indicated by the double arrow TN is the thickness of the sidewall layer 6 at the inner end FN of the zone ZF. The length indicated by the double arrow TG is the thickness of the sidewall layer 6 at the outer end FG of the zone ZF. The length indicated by the double arrow TC is the thickness of the sidewall layer 6 at the center FC of the zone ZF. The thicknesses TN, TG, and TC are measured along a normal to the carcass 10. In the present invention, the average thickness F of the sidewall layer 6 in the zone ZF is expressed as the average value of the thickness TN, the thickness TG, and the thickness TC.

[0080] The inventors of the present invention have noticed that the width BW of the belt affects the contour of the carcass (more specifically, the ply body), and that if the contour of the carcass becomes distorted, the distortion occurring in the bead portion increases, and the durability of the tire decreases. While adjusting the width BW of the belt, the inventors have conducted extensive research into what average thickness F the sidewall layer in the aforementioned zone ZF must have in order for the tire to withstand the action of a high load as represented by the aforementioned formula (1) or (2). As a result, they have obtained the following relational expression for the average thickness F of the sidewall layer 6 in the zone ZF.

[0081] That is, the average thickness F of the sidewall layer 6 in the zone ZF satisfies the following formula (3), which is expressed using a constant B, the cross-sectional width SW of the tire 2, and the width BW of the belt 12 obtained in the reference state of the tire 2. Formula (3): 380×(BW / SW-B) 2 +3.5≦F≦380×(BW / SW-B) 2 +5.5 The average thickness F, cross-sectional width SW, and width BW are all in millimeters (mm).

[0082] Furthermore, the constant B satisfies the following equation (4) expressed using the aspect ratio RA of the tire 2. Formula (2): B=0.84×(-0.49×RA / 100+1.22) In addition, the aspect ratio RA in equation (2) is the "nominal aspect ratio." For example, if the tire size is 245 / 45R18, the nominal aspect ratio RA of this tire is 45%. In this case, the constant B is 0.84.

[0083] Average thickness F is 380 × (BW / SW-B) 2 If it is less than +3.5, the sidewall layer 6 in the zone ZF becomes too thin and the tire may not be able to withstand the action of a high load. Average thickness F is 380 × (BW / SW-B) 2 If it is greater than +5.5, there is a concern that the sidewall layer 6 in the zone ZF will be too thick, and the significance of adopting the carcass 10 consisting of one carcass ply 42 for weight reduction will be lost. However, when the average thickness F satisfies the above-mentioned formula (3), the width BW of the belt 12 and the thickness of the sidewall layer 6 in the zone ZF are well balanced. The average thickness F of the sidewall layer 6 is set to match the width BW of the belt 12. In other words, the tire 2 can optimize the average thickness F while reducing the compressive strain generated in the carcass 10. Because the average thickness F is set to a required thickness, the tire 2 can be made lighter. Because the compressive strain generated in the carcass 10 is reduced, the tire 2 can withstand the action of a high load. In particular, by setting the ratio (BW / SW) of the belt width BW to the cross-sectional width SW of the tire 2 to be equal to the constant B expressed by formula (2), the tire 2 can withstand the action of a high load as expressed by formula (1) or (2) even when the average thickness F of the sidewall layer 6 in the zone ZF is set to 3.5 to 5.5 mm.

[0084] Although the tire 2 employs a carcass 10 consisting of a single carcass ply 48, the sidewall layer 6 in the bead portion can be effectively thinned while ensuring the rigidity required to withstand the action of a high load. The tire 2 can achieve improved durability without increasing rolling resistance. From this viewpoint, it is preferable that the average thickness F of the sidewall layer in the zone ZF satisfies the above-mentioned formula (3) and the constant B satisfies the above-mentioned formula (4).

[0085] As is clear from the above description, the present invention provides a tire 2 that can achieve improved durability without increasing rolling resistance. [Example]

[0086] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0087] [Examples 1-2 and Comparative Examples 1-3] Tires of Examples 1-2 and Comparative Examples 1-3 (tire size=245 / 45R18) having the basic structure shown in FIG. 1 and the specifications shown in Table 1 below were obtained. In Table 1, the column represented by "Cb" indicates the number of carcass plies located radially inside the bead. Since the carcasses of Example 1-2 and Comparative Example 1 have a 1-0UHTU structure, the number Cb of carcass plies located radially inside the bead is 1. The ratio BW / SW of the belt width BW to the tire section width SW was 0.95.

[0088] Comparative Example 2 used a carcass with a 1-0HTU structure. The carcass of Comparative Example 1 was composed of one carcass ply, and the end of the turned-up portion was positioned 5 mm radially outward from the maximum width position. The end of the turned-up portion did not overlap with the end of the belt. The number Cb of carcass plies positioned radially inward of the bead was one.

[0089] Comparative Example 3 employed a carcass with a 2-0HTU structure. The carcass of Comparative Example 2 was composed of two carcass plies, with the end of the turned-up portion located on the axially inner side being positioned 30 mm radially outward from the maximum width position, and the end of the turned-up portion located on the axially outer side being positioned 5 mm radially outward from the maximum width position. Neither end of the two turned-up portions overlaps with the end of the belt. The number Cb of carcass plies located radially inward of the bead was two.

[0090] [Rolling resistance (RRC)] Using a rolling resistance tester, the rolling resistance coefficient (RRC) was measured when the prototype tire ran on a drum at a speed of 80 km / h under the following conditions. The results are shown in the "RRC" column in Table 1 below as an index, with Example 1 given a score of 10. The higher the value, the lower the rolling resistance of the tire. Rim: 8.0 inches Internal pressure: 250kPa Vertical load: 6.86kN

[0091] [Durability] The prototype tire was mounted on a rim (size = 8.0 inches) and inflated with air to an internal pressure of 360 kPa. This tire was mounted on a drum-type running test machine. A vertical load of 8.58 kN was applied to the tire, and the tire was run on a drum (radius = 1.7 m) at a speed of 100 km / h. The running distance until damage to the tire was confirmed was measured. The results are shown in the "Durability" column in Table 1 below as an index, with Example 1 being given a score of 10. The higher the index, the better the durability.

[0092] [Table 1]

[0093] As shown in Table 1, in the examples, improvement in durability was achieved without an increase in rolling resistance. From these evaluation results, the superiority of the present invention is clear. [Industrial Applicability]

[0094] The above-described technology that can achieve improved durability without increasing rolling resistance can be applied to various tires.

[0095] [Note] The present invention includes the following aspects.

[0096] [1] A tire having a load index LI that satisfies the relationship shown in the following formula (1) or the following formula (2), a pair of beads; a carcass that spans between the pair of beads; a pair of sidewall layers positioned axially outward of the carcass; a tread located radially outward of the carcass and in contact with a road surface; a belt including a large number of parallel belt cords; a band including a spirally wound band cord; Equipped with The belt is laminated on the carcass radially inside the tread, the band is located between the tread and the belt in the radial direction, The carcass is composed of one carcass ply including a large number of carcass cords arranged in parallel, The carcass ply includes a ply body and a pair of turned-up portions, The ply body spans between a pair of the beads, Each of the turned-up portions is continuous with the ply body and turned up from the inside toward the outside in the axial direction at each of the beads, an end of the folded portion is located axially inside the end of the belt, a first normal line is a normal line to the carcass that passes through an intersection point between a first imaginary line that passes through an end of the belt and extends in the axial direction and an outer surface of the tire; a normal line to the carcass that passes through a maximum width position of the tire is a second normal line, A tire in which a ratio D / E of a thickness D from the carcass to the outer surface of the tire along the first normal line to a thickness E from the carcass to the outer surface of the tire along the second normal line is 1 or greater and 2 or less. Formula (1): LIx≦LI≦LIx+4 Equation (2): LI = LIh LIx in the formula (1) and LIh in the formula (2) are as follows: LIx: The load index of an EXTRA LOAD CAPACITY type tire specified in the ETRTO 2019 standard manual, which has the same dimensional and structural characteristics as the dimensional and structural characteristics included in the tire designation of the tire. LIh: The load index of a HIGH LOAD CAPACITY type tire specified in the ETRTO 2021 standard manual, which has the same dimensional and structural characteristics as the dimensional and structural characteristics included in the tire designation of the tire. [2] A ratio TCa / TA of a thickness TCa of the carcass at the equatorial plane of the tire to a thickness TA of the tire at the equatorial plane of the tire is 0.03 or more and 0.1 or less, a ratio TCh / T1 of a thickness TCh of the carcass along the first normal line to a thickness T1 of the tire along the first normal line is 0.05 or more and 0.35 or less; The tire according to [1] above, wherein a ratio TCe / T2 of a thickness TCe of the carcass along the second normal line to a thickness T2 of the tire along the second normal line is 0.06 or greater and 0.55 or less. [3] The tire according to the above-mentioned [2], wherein the difference between the ratio TCe / T2 and the ratio TCh / T1 (TCe / T2-TCh / T1) is 0.0 or more and 0.5 or less. [4] The tire according to any one of [1] to [3] above, wherein the outer diameter of the carcass cord is 0.6 mm or more and 0.8 mm or less. [5] The average thickness F of the sidewall layer in a zone from 20 mm to 30 mm in the radial direction from the bead base line satisfies the following formula (3), which is expressed using a constant B, and the cross-sectional width SW of the tire and the width BW of the belt, which are obtained under a standard condition in which the tire is mounted on a regular rim, the internal pressure of the tire is adjusted to 290 kPa, and no load is applied to the tire. The tire according to any one of the above [1] to [4], wherein the constant B satisfies the following formula (4) expressed using the aspect ratio RA of the tire. Formula (3): 380×(BW / SW-B) 2 +3.5≦F≦380×(BW / SW-B) 2 +5.5 Equation (4): B=0.84×(-0.49×RA / 100+1.22) [Explanation of symbols]

[0097] 2. Tires 2G: Outer surface of tire 2 2N: Inner surface of tire 2 4. Tread 6. Sidewall layer 8. Bead 10. Carcass 12. Belt 14...Band 20. Insulation 34 Sidewall body 36. Clinch 42···Carcass ply 44···Ply body 46 Folded part 48···Carcass cord 58 Belt cord 62...Full Band

Claims

1. A tire having a load index LI that satisfies the relationship shown in the following formula (1) or the following formula (2), a pair of beads; a carcass that spans between the pair of beads; a pair of sidewall layers positioned axially outward of the carcass; a tread located radially outward of the carcass and in contact with a road surface; a belt including a large number of parallel belt cords; a band including a spirally wound band cord; Equipped with The belt is laminated on the carcass radially inside the tread, the band is located between the tread and the belt in the radial direction, The carcass is composed of one carcass ply including a large number of carcass cords arranged in parallel, The carcass ply includes a ply body and a pair of turned-up portions, The ply body spans between a pair of the beads, Each of the turned-up portions is continuous with the ply body and turned up from the inside toward the outside in the axial direction at each of the beads, an end of the folded portion is located axially inside the end of the belt, a first normal line is a normal line to the carcass that passes through an intersection point between a first imaginary line that passes through an end of the belt and extends in the axial direction and an outer surface of the tire; a normal line to the carcass that passes through a maximum width position of the tire is a second normal line, a ratio D / E of a thickness D from the carcass to the outer surface of the tire along the first normal line to a thickness E from the carcass to the outer surface of the tire along the second normal line is 1 or greater and 2 or less; tire. Formula (1): LIx≦LI≦LIx+4 Formula (2): LI=LIh LIx in the formula (1) and LIh in the formula (2) are as follows: LIx: Load index of a tire of EXTRA LOAD CAPACITY type specified in the ETRTO 2019 standard manual, having the same dimensional and structural characteristics as those included in the tire designation of the tire. LIh: Load index of a tire of a high load capacity type defined in the ETRTO 2021 standard manual, having the same dimensional and structural characteristics as those included in the tire designation of the tire.

2. a ratio TCa / TA of a thickness TCa of the carcass at the equatorial plane of the tire to a thickness TA of the tire at the equatorial plane of the tire is 0.03 or greater and 0.1 or less, a ratio TCh / T1 of a thickness TCh of the carcass along the first normal line to a thickness T1 of the tire along the first normal line is 0.05 or greater and 0.35 or less, a ratio TCe / T2 of a thickness TCe of the carcass along the second normal line to a thickness T2 of the tire along the second normal line is 0.06 or more and 0.55 or less; 2. The tire of claim 1.

3. a difference (TCe / T2-TCh / T1) between the ratio TCe / T2 and the ratio TCh / T1 is 0.0 or more and 0.5 or less; 3. The tire of claim 2.

4. The outer diameter of the carcass cord is 0.6 mm or more and 0.8 mm or less.

2. The tire of claim 1.

5. an average thickness F of the sidewall layer in a zone from 20 mm to 30 mm in the radial direction from a bead base line satisfies the following formula (3), which is expressed using a constant B, and a cross-sectional width SW of the tire and a width BW of the belt, which are obtained under a standard condition in which the tire is mounted on a regular rim, the internal pressure of the tire is adjusted to 290 kPa, and no load is applied to the tire; The constant B satisfies the following formula (4) expressed using the aspect ratio RA of the tire:

5. A tire according to any one of claims 1 to 4. Equation (3): 380 × (BW / SW - B) ２ +3.5 ≤ F ≤ 380 × (BW / SW - B) ２ +5.5 Formula (4): B=0.84×(-0.49×RA / 100+1.22)

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