Pneumatic tires

Abstract

To provide a pneumatic tire 2 with an excellent balance between low cost and durability.SOLUTION: A tire 2 has a carcass 10, a right bead 8a and a left bead 8b. The carcass 10 has a bias structure. The carcass 10 includes a first ply 18 and a second ply 20. The first ply 18 is folded back at the right bead 8a and the left bead 8b. The first ply 18 has a crown-overlap structure. The second ply 20 is folded back at the right bead 8a and the left bead 8b. The second ply 20 has a crown-overlap structure.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a pneumatic tire, and more particularly to an improvement in the carcass of the tire. [Background technology]

[0002] Pneumatic tires used on industrial vehicles such as forklifts are required to be low cost. Since industrial vehicles run at low speeds, high performance at high speeds is not required for these tires. For these reasons, so-called bias tires are used for industrial vehicles. An example of a bias tire is disclosed in JP2015-9752A. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP2015-9752A Summary of the Invention [Problem to be solved by the invention]

[0004] In a typical industrial tire, the carcass has multiple plies. In this carcass, multiple ply ends are concentrated in the side portion of the tire. When the tire runs, the side portion repeatedly bends and restores its shape. Stress is concentrated in the ply ends present in the side portion. In this tire, ply separation is likely to occur. This tire has poor durability.

[0005] An object of the present invention is to provide a pneumatic tire that has an excellent balance between low cost and durability. [Means for solving the problem]

[0006] A pneumatic tire according to the present invention has a right bead, a left bead, a carcass, and a tread. The carcass has a first ply and a second ply. The first ply includes a plurality of cords arranged in parallel and each inclined with respect to the circumferential direction. The second ply includes a plurality of cords arranged in parallel and each inclined with respect to the circumferential direction. The first ply is turned up at the right bead and the left bead, thereby forming a first main portion, a first right turn-up portion, and a first left turn-up portion. The second ply is turned up at the right bead and the left bead, thereby forming a second main portion, a second right turn-up portion, and a second left turn-up portion. An end of the first right turn-up portion is located to the left of the equatorial plane of the tire. An end of the first left turn-up portion is located to the right of the equatorial plane. An end of the second right turn-up portion is located to the left of the equatorial plane. An end of the second left turn-up portion is located to the right of the equatorial plane.

[0007] Preferably, the inclination direction of the cords in the second main portion with respect to the equator plane is opposite to the inclination direction of the cords in the first main portion with respect to the equator plane.

[0008] Preferably, an end of the first right folded portion and an end of the second right folded portion are spaced apart. Preferably, an end of the first left folded portion and an end of the second left folded portion are spaced apart. Preferably, a distance between an end of the first right folded portion and an end of the second right folded portion is 10 mm or more. Preferably, a distance between an end of the first left folded portion and an end of the second left folded portion is 10 mm or more.

[0009] Preferably, the ratio of the height of the end of the first right turned-up portion to the height of the tire is 70% or more. Preferably, the ratio of the height of the end of the first left turned-up portion to the height of the tire is 70% or more. Preferably, the ratio of the height of the end of the second right turned-up portion to the height of the tire is 70% or more. Preferably, the ratio of the height of the end of the second left turned-up portion to the height of the tire is 70% or more.

[0010] Preferably, a ratio of a distance from the equatorial plane to an end of the first right turn-up portion to a half-width of the tread is 40% or more. Preferably, a ratio of a distance from the equatorial plane to an end of the first left turn-up portion to a half-width of the tread is 40% or more. Preferably, a ratio of a distance from the equatorial plane to an end of the second right turn-up portion to a half-width of the tread is 40% or more. Preferably, a ratio of a distance from the equatorial plane to an end of the second left turn-up portion to a half-width of the tread is 40% or more.

[0011] Preferably, on the equatorial plane, from the inner side to the outer side in the radial direction of the tire, First main part, The second main part, Second right fold, Second left fold, First right fold and First left fold But they are lined up in this order.

[0012] On the equatorial plane, from the inside to the outside in the radial direction of the tire, First main part, Second main part, Second left fold, Second right fold, First left fold and First right fold However, they may be arranged in this order.

[0013] On the equatorial plane, from the inside to the outside in the radial direction of the tire, First main part, Second main part, Second right fold, First right fold, Second left fold and First left fold However, they may be arranged in this order.

[0014] On the equatorial plane, from the inside to the outside in the radial direction of the tire, First main part, The second main part, Second left fold, First left fold, Second right fold and First right fold However, they may be arranged in this order. Effect of the Invention

[0015] In the pneumatic tire according to the present invention, separation of the ply of the carcass is unlikely to occur. The tire has excellent durability. Furthermore, the tire can be obtained at low cost. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a cross-sectional view showing a portion of a pneumatic tire according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic diagram showing the carcass of the tire of FIG. 1 together with the beads. [Diagram 3] FIG. 3 is an enlarged perspective cross-sectional view of a portion of the first ply of the carcass of FIG. 2. FIG. [Figure 4] FIG. 4 is an enlarged cross-sectional view showing a portion of the first ply of FIG. [Diagram 5] 5 is an enlarged cross-sectional perspective view of a portion of the second ply of the carcass of FIG. 2. FIG. [Figure 6] FIG. 6 is an enlarged exploded perspective view of a portion of the carcass of FIG. 2. FIG. [Figure 7] FIG. 7 is an enlarged view of a portion of the tire of FIG. [Figure 8] FIG. 8 is an enlarged view showing another part of the tire shown in FIG. [Figure 9] FIG. 9 is a schematic diagram showing a carcass of a pneumatic tire according to another embodiment of the present invention together with a bead. [Figure 10] FIG. 10 is an enlarged exploded perspective view of a portion of the carcass of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, the present invention will be described in detail based on preferred embodiments with reference to the drawings as appropriate.

[0018] FIG. 1 shows a pneumatic tire 2. FIG. 1 shows a cross section along a plane including the axis of rotation of the tire 2. In FIG. 1, the up-down direction is the radial direction of the tire 2, the left-right direction is the axial direction of the tire 2, and the direction perpendicular to the paper surface is the circumferential direction of the tire 2. In FIG. 1, the center line CL coincides with the equatorial plane of the tire 2. In FIG. 1, the imaginary line BL represents a baseline. The baseline BL defines the diameter of the rim on which the tire 2 is mounted. The arrow Ht represents the height of the edge of the tread 4 (described in detail later) from the baseline BL. The height Ht is measured along the radial direction. The arrow Tw represents the width of the tread 4. The width Tw is measured along the axial direction.

[0019] The tire 2 has a tread 4, a pair of sidewalls 6, a pair of beads 8, and a carcass 10. A tube (not shown) is inserted into the tire 2. The tire 2 may be of a tubeless type. The tire 2 is mounted on an industrial vehicle such as a forklift.

[0020] The tread 4 has a tread surface 12 that comes into contact with the road surface. A plurality of grooves 13 are formed in the tread 4. Each groove 13 generally extends in the axial direction. These grooves 13 form a tread pattern. The tread 4 is made of a crosslinked rubber that has excellent abrasion resistance, heat resistance, and grip. The tread 4 may have a base layer and a cap layer. The tread 4 may have three or more layers.

[0021] Each sidewall 6 extends radially inwardly from an end of the tread 4. A radially outer end of each sidewall 6 is joined to the tread 4. Each sidewall 6 is formed of a crosslinked rubber having excellent cut resistance and weather resistance. Each sidewall 6 prevents damage to the carcass 10. The material of the sidewall 6 may be the same as the material of the tread 4. Each sidewall 6 may have a clinch in its radially inner zone. The clinch may be formed of a crosslinked rubber having excellent abrasion resistance.

[0022] Each bead 8 is located axially and radially inward of the sidewall 6. The bead 8 includes a core 14 and a filler 16 extending radially outward from the core 14. The core 14 is ring-shaped and includes a wound inelastic wire. The wire is typically made of steel. The filler 16 tapers radially outward. The filler 16 is made of high-hardness crosslinked rubber. The filler 16 may have a shape with little change in thickness along the radial direction (in other words, a sheet shape). In this embodiment, the tire 2 has a right bead 8a and a left bead 8b.

[0023] The carcass 10 is disposed between the beads 8 on both sides and extends along the tread 4 and the sidewalls 6 .

[0024] Fig. 2 is a schematic diagram showing the carcass 10 of the tire 2 in Fig. 1 together with beads 8a, 8b. The carcass 10 has a first ply 18 and a second ply 20. In Fig. 2, for convenience of explanation, the first ply 18 is drawn with a solid line, and the second ply 20 is drawn with a dotted line. The number of plies in this carcass 10 is two. The carcass 10 may have three or more plies. From the viewpoint of material cost, the number of plies is preferably two.

[0025] The first ply 18 is turned up at the right bead 8a and the left bead 8b. By this turning up, a first main portion 22, a first right turn-up portion 24, and a first left turn-up portion 26 are formed in the first ply 18. The first main portion 22 extends from the right bead 8a to the left bead 8b. The first right turn-up portion 24 extends from the right bead 8a to the end E1a. The end E1a of the first right turn-up portion 24 is located to the left of the equatorial plane CL. In other words, the first right turn-up portion 24 straddles the equatorial plane CL. The first left turn-up portion 26 extends from the left bead 8b to the end E1b. The end E1b of the first left turn-up portion 26 is located to the right of the equatorial plane CL. In other words, the first left turn-up portion 26 straddles the equatorial plane CL. In the first ply 18, the first right turn-up portion 24 and the first left turn-up portion 26 overlap in the radial direction. In other words, the first ply 18 has a crown-overlap structure.

[0026] The second ply 20 is turned up at the right bead 8a and the left bead 8b. By this turning up, the second main portion 28, the second right turn-up portion 30, and the second left turn-up portion 32 are formed in the second ply 20. The second main portion 28 extends from the right bead 8a to the left bead 8b. The second right turn-up portion 30 extends from the right bead 8a to the end E2a. The end E2a of the second right turn-up portion 30 is located to the left of the equatorial plane CL. In other words, the second right turn-up portion 30 straddles the equatorial plane CL. The second left turn-up portion 32 extends from the left bead 8b to the end E2b. The end E2b of the second left turn-up portion 32 is located to the right of the equatorial plane CL. In other words, the second left turn-up portion 32 straddles the equatorial plane CL. In the second ply 20, the second right turned-up portion 30 and the second left turned-up portion 32 overlap in the radial direction. In other words, the second ply 20 has a crown-overlap structure.

[0027] In the carcass 10, on the equatorial plane CL, from the inside to the outside in the radial direction, First main portion 22, A second main portion 28, Second right folded portion 30; A second left folded portion 32; First right folded part 24 and First left fold 26 But they are listed in this order.

[0028] FIG. 3 is a cross-sectional perspective view showing an enlarged portion of the first ply 18 of the carcass 10 in FIG. 2. FIG. 3 shows the vicinity of the equatorial plane CL of the first main portion 22. The first ply 18 has a large number of cords 34. Each cord 34 is inclined with respect to the circumferential direction (Z direction). The dashed line in FIG. 3 is the center line of the cord 34. In FIG. 2, the arrow α indicates the inclination angle of the cord 34 with respect to the circumferential direction. The angle α has a positive value. The angle α is preferably +15° (degrees) or more and +45° or less. The preferred cords 34 are twisted wires of organic fibers. Preferred organic fibers include polyester fibers, nylon fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers.

[0029] Fig. 4 is an enlarged cross-sectional view showing a part of the first ply 18 in Fig. 3. Fig. 4 shows the first ply 18 before it is assembled with other members. The cross section of Fig. 4 is perpendicular to the extension direction of the cords 34. As shown in Fig. 4, the first ply 18 has a topping rubber 36 together with the cords 34. The cords 34 are generally covered with the topping rubber 36. The cords 34 are spaced apart from the adjacent cords 34. The topping rubber 36 is present between the cords 34 and the adjacent cords 34.

[0030] 4, arrow Dc represents the diameter of the cord 34, arrow Tp represents the thickness of the first ply 18, arrow Pc represents the pitch of the cord 34, and arrow Lc represents the distance between the cords 34. In a typical tire 2, the ratio of the diameter Dc to the thickness Tp (Dc / Tp) is 0.75 or more and 0.90 or less. In a typical tire 2, the ratio of the distance Lc to the pitch Pc (Lc / Pc) is 0.15 or more and 0.50 or less.

[0031] FIG. 5 is a cross-sectional perspective view showing an enlarged portion of the second ply 20 of the carcass 10 in FIG. 2. FIG. 5 shows the vicinity of the equatorial plane CL of the second main portion 28. The second ply 20 has a large number of cords 34. Each cord 34 is inclined with respect to the circumferential direction (Z direction). The dashed line in FIG. 5 is the center line of the cord 34. In FIG. 2, the arrow β indicates the inclination angle of the cord 34 with respect to the circumferential direction. The angle β has a negative value. The inclination direction of the cord 34 in the second main portion 28 with respect to the equatorial plane CL is opposite to the inclination direction of the cord 34 in the first main portion 22 with respect to the equatorial plane CL. The angle β is preferably -45° (degrees) or more and -15° or less. In other words, the absolute value of the angle β is preferably 15° or more and 45° or less. In this embodiment, the specifications of the second ply 20 except for the angle of the cord 34 are the same as those of the first ply 18. That is, the material, diameter Dc, thickness Tp, pitch Pc and distance Lc of the cord 34 of the second ply 20 are the same as those of the first ply 18 .

[0032] Fig. 6 is an exploded perspective view showing an enlarged portion of the carcass 10 in Fig. 2. Fig. 6 shows the vicinity of the equatorial plane CL of the carcass 10. As described above, in this carcass 10, the first main portion 22 is present at the innermost position in the radial direction. As shown in Fig. 3, the inclination angle of the cords 34 of this first main portion 22 is "positive (P)". On the outer side of this first main portion 22, the second main portion 28 is present. As shown in Fig. 5, the inclination angle of the cords 34 of this second main portion 28 is "negative (N)". This carcass 10 has a bias structure.

[0033] A second right turned-up portion 30 exists on the outer side of the second main portion 28. The second right turned-up portion 30 is formed by turning up the second ply 20 at the right bead 8a, and therefore the inclination direction of the cords 34 in this second right turned-up portion 30 is opposite to the inclination direction of the cords 34 in the second main portion 28. The inclination angle of the cords 34 in this second right turned-up portion 30 is "positive".

[0034] A second left turned-up portion 32 exists on the outer side of this second right turned-up portion 30. The second left turned-up portion 32 is formed by turning up the second ply 20 at the left bead 8b, so the inclination direction of the cords 34 of this second left turned-up portion 32 is opposite to the inclination direction of the cords 34 of the second main portion 28. The inclination angle of the cords 34 of this second left turned-up portion 32 is "positive".

[0035] The first right turned-up portion 24 exists on the outer side of the second left turned-up portion 32. The first right turned-up portion 24 is formed by turning up the first ply 18 at the right bead 8a, and therefore the inclination direction of the cords 34 in this first right turned-up portion 24 is opposite to the inclination direction of the cords 34 in the first main portion 22. The inclination angle of the cords 34 in this first right turned-up portion 24 is "negative".

[0036] The first left turned-up portion 26 is present on the outer side of the first right turned-up portion 24. The first left turned-up portion 26 is formed by turning up the first ply 18 at the left bead 8b, so the inclination direction of the cords 34 in this first left turned-up portion 26 is opposite to the inclination direction of the cords 34 in the first main portion 22. The inclination angle of the cords 34 in this first left turned-up portion 26 is "negative".

[0037] In the carcass 10, on the equatorial plane CL, from the inner side to the outer side in the radial direction, Layer 22, with a code 34 tilt angle of "positive"; Layer 28, where the inclination angle of code 34 is "negative", Layer 30, where the inclination angle of code 34 is "positive"; Layer 32, where the inclination angle of code 34 is "positive"; Layer 24, where the inclination angle of Code 34 is "negative" and Layer 26 with a negative inclination angle of Code 34 are arranged in this order. The total number of layers is 6. The number of layers in which the inclination angle of the cords 34 is "positive" is 3. The number of layers in which the inclination angle of the cords 34 is "negative" is 3. The number of layers in which the inclination angle of the cords 34 is "negative" is the same as the number of layers in which the inclination angle of the cords 34 is "positive". This carcass 10 can contribute to uniformity. In a tire 2 having this carcass 10, uneven wear can be suppressed.

[0038] In this carcass 10, even though the number of plies is only 2, the number of layers in the vicinity of the equatorial plane CL is 6. This tire 2 can be obtained at low cost, and is excellent in stiffness and durability.

[0039] As is clear from FIG. 1, an end E1a of the first right folded portion 24 is spaced apart from the sidewall 6. An end E1b of the first left folded portion 26 is spaced apart from the sidewall 6. An end E2a of the second right folded portion 30 is spaced apart from the sidewall 6. An end E2b of the second left folded portion 32 is spaced apart from the sidewall 6. When the tire 2 runs, the sidewall 6 repeatedly bends and restores its original shape. Stress is concentrated on the sidewall 6. Since each end is spaced apart from the sidewall 6, even if stress is concentrated on the sidewall 6, peeling of the ply near the ends is suppressed. This tire 2 has excellent durability.

[0040] An end E2a of the second right turned-up portion 30 is spaced apart from an end E1a of the first right turned-up portion 24. An end E2b of the second left turned-up portion 32 is spaced apart from an end E1b of the first left turned-up portion 26. In the tire 2, stress concentration at the ends can be suppressed. The tire 2 has excellent durability.

[0041] As is clear from FIG. 2, end E1a of the first right turned-up portion 24 is covered by the first left turned-up portion 26. This end E1a is not easily peeled off. End E2a of the second right turned-up portion 30 is covered by the second left turned-up portion 32. This end E2a is not easily peeled off. End E2b of the second left turned-up portion 32 is covered by the first right turned-up portion 24. This end E2b is not easily peeled off. Only end E1b of the first left turned-up portion 26 is exposed on the surface of the belt. The number of exposed ends is only one. This tire 2 has excellent durability.

[0042] Fig. 7 is an enlarged view showing a part of the tire 2 in Fig. 1. Fig. 7 shows a portion located to the right of the equatorial plane CL. In Fig. 7, an arrow Lb indicates the distance between the end E1b of the first left folded-back portion 26 and the end E2b of the second left folded-back portion 32. In a tire 2 having a large distance Lb, stress is dispersed. This tire 2 has excellent durability. From the viewpoint of durability, the distance Lb is preferably 10 mm or more, more preferably 15 mm or more, and particularly preferably 18 mm or more. The distance Lb is preferably 40 mm or less.

[0043] In Fig. 7, an arrow H1b indicates the height of the end E1b of the first left folded portion 26 from the baseline BL. The end E1b having a large height H1b is less susceptible to the bending of the sidewall 6. A tire 2 having a large height H1b has excellent durability. From the viewpoint of durability, the ratio of the height H1b to the height Ht of the end of the tread 4 is preferably equal to or greater than 70%, more preferably equal to or greater than 75%, and particularly preferably equal to or greater than 80%. This ratio is preferably equal to or less than 90%.

[0044] In Fig. 7, the arrow H2b indicates the height of the end E2b of the second left folded-back portion 32 from the baseline BL. The end E2b having a large height H2b is less susceptible to the bending of the sidewall 6. A tire 2 having a large height H2b has excellent durability. From the viewpoint of durability, the ratio of the height H2b to the height Ht of the end of the tread 4 is preferably 70% or more, more preferably 75% or more, and particularly preferably 80% or more. This ratio is preferably 90% or less.

[0045] 7, an arrow W1b indicates the distance from the equatorial plane CL to the end E1b of the first left folded-back portion 26. A tire 2 having a large distance W1b has excellent rigidity and durability. In terms of rigidity and durability, the ratio of the distance W1b to the half width Wt / 2 of the tread 4 is preferably equal to or greater than 40%, more preferably equal to or greater than 50%, and particularly preferably equal to or greater than 55%. This ratio is preferably equal to or less than 90%.

[0046] In Fig. 7, an arrow W2b indicates the distance from the equatorial plane CL to the end E2b of the second left folded-back portion 32. A tire 2 having a large distance W2b has excellent rigidity and durability. In terms of rigidity and durability, the ratio of the distance W2b to the half width Wt / 2 of the tread 4 is preferably equal to or greater than 40%, more preferably equal to or greater than 50%, and particularly preferably equal to or greater than 55%. This ratio is preferably equal to or less than 90%.

[0047] Fig. 8 is an enlarged view showing another part of the tire 2 in Fig. 1. Fig. 8 shows a portion located to the left of the equatorial plane CL. In Fig. 8, an arrow La indicates the distance between an end E1a of the first right folded-back portion 24 and an end E2a of the second left folded-back portion 32. In a tire 2 having a large distance La, stress is dispersed. This tire 2 has excellent durability. From the viewpoint of durability, the distance La is preferably equal to or greater than 10 mm, more preferably equal to or greater than 15 mm, and particularly preferably equal to or greater than 18 mm. The distance La is preferably equal to or less than 40 mm.

[0048] In Fig. 8, an arrow H1a indicates the height of the end E1a of the first right turn-up portion 24 from the baseline BL. The end E1a with a large height H1a is less susceptible to the bending of the sidewall 6. A tire 2 with a large height H1a has excellent durability. From the viewpoint of durability, the ratio of the height H1a to the height Ht of the end of the tread 4 is preferably 70% or more, more preferably 75% or more, and particularly preferably 80% or more. This ratio is preferably 90% or less.

[0049] In Fig. 8, an arrow H2a indicates the height of an end E2a of the second right folded-back portion 30 from the baseline BL. The end E2a having a large height H2a is less susceptible to the bending of the sidewall 6. A tire 2 having a large height H2a has excellent durability. From the viewpoint of durability, the ratio of the height H2a to the height Ht of the end of the tread 4 is preferably 70% or more, more preferably 75% or more, and particularly preferably 80% or more. This ratio is preferably 90% or less.

[0050] In Fig. 8, an arrow W1a indicates the distance from the equatorial plane CL to the end E1a of the first right folded-back portion 24. A tire 2 having a large distance W1a has excellent rigidity and durability. In terms of rigidity and durability, the ratio of the distance W1a to the half width Wt / 2 of the tread 4 is preferably equal to or greater than 40%, more preferably equal to or greater than 50%, and particularly preferably equal to or greater than 55%. This ratio is preferably equal to or less than 90%.

[0051] In Fig. 8, an arrow W2a indicates the distance from the equatorial plane CL to the end E2a of the second right folded-back portion 30. A tire 2 having a large distance W2a has excellent rigidity and durability. In terms of rigidity and durability, the ratio of the distance W2a to the half width Wt / 2 of the tread 4 is preferably equal to or greater than 40%, more preferably equal to or greater than 50%, and particularly preferably equal to or greater than 55%. This ratio is preferably equal to or less than 90%.

[0052] The carcass 10 includes four ends E1a, E1b, E2a, and E2b. Of these four ends, the ratio of the height Hmin of the end having the smallest height from the baseline BL to the height Ht of the end of the tread 4 is preferably 70% or more, more preferably 75% or more, and particularly preferably 80% or more. Of these four ends, the ratio of the distance Wmin of the end having the smallest distance from the equatorial plane CL to the half width Wt / 2 of the tread 4 is preferably 40% or more, more preferably 50% or more, and particularly preferably 55% or more.

[0053] Like the inclination angle of the cord 34 in the first main portion 22, the inclination angle of the cord 34 in the second main portion 28 may be "positive". In this case, the inclination angle of the cord 34 in the second right turned-up portion 30 is "negative", and the inclination angle of the cord 34 in the second left turned-up portion 32 is "negative". In this carcass 10, on the equatorial plane CL, from the inside to the outside in the radial direction, Layer 22, with a code 34 tilt angle of "positive"; Layer 28, with a code 34 tilt angle of "positive"; Layer 30, where the inclination angle of code 34 is "negative"; Layer 32, where the inclination angle of code 34 is "negative"; Layer 24, where the inclination angle of Code 34 is "negative" and Layer 26 with a negative inclination angle of Code 34 The number of layers with a "positive" tilt angle of Code 34 is 2. The number of layers with a "negative" tilt angle of Code 34 is 4.

[0054] Like the inclination angle of the cords 34 in the second main portion 28, the inclination angle of the cords 34 in the first main portion 22 may be "negative". In this case, the inclination angle of the cords 34 in the first right turned-up portion 24 is "positive", and the inclination angle of the cords 34 in the first left turned-up portion 26 is "positive". In this carcass 10, on the equatorial plane CL, from the inside to the outside in the radial direction, Layer 22, where the inclination angle of code 34 is "negative"; Layer 28, where the inclination angle of code 34 is "negative", Layer 30, where the inclination angle of code 34 is "positive"; Layer 32, where the inclination angle of code 34 is "positive"; Layer 24 with a "positive" tilt angle of Code 34 and Layer 26 with a positive inclination angle of Code 34 The number of layers with a "positive" tilt angle of Code 34 is 4. The number of layers with a "negative" tilt angle of Code 34 is 2.

[0055] The tire 2 may have a shape that is a mirror image of the shape shown in Fig. 1 with respect to the equatorial plane CL. In the carcass 10 of the tire 2, on the equatorial plane CL, First main part, The second main part, Second left fold, Second right fold, First left fold and First right fold In this carcass 10, peeling at each end can be suppressed.

[0056] In the present invention, the dimensions and angles of each component of the tire 2 are measured in a state where the tire 2 is mounted on a regular rim and filled with air so as to have a regular internal pressure. No load is applied to the tire 2 during measurement. In this specification, regular rim means a rim defined in the standard on which the tire 2 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 regular rims. In this specification, regular internal pressure means an internal pressure defined in the standard on which the tire 2 is based. The "maximum air pressure" in the JATMA standard, the "maximum value" listed in "TIRE LOAD LIMITSAT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "INFLATION PRESSURE" in the ETRTO standard are regular internal pressures.

[0057] FIG. 9 is a schematic diagram showing a carcass 38 of a pneumatic tire according to another embodiment of the present invention. The structures of the members of this tire other than the carcass 38 are the same as those of the tire shown in FIG. 1. This carcass 38 has a first ply 40 and a second ply 42. In FIG. 9, for convenience of explanation, the first ply 40 is drawn with a solid line, and the second ply 42 is drawn with a dotted line. The number of plies in this carcass 38 is two. The carcass 38 may have three or more plies. From the viewpoint of material cost, the number of plies is preferably two. The structure of the first ply 40 is the same as that of the first ply 18 shown in FIG. 3. The structure of the second ply 42 is the same as that of the second ply 20 shown in FIG. 5.

[0058] The first ply 40 is turned up at the right bead 8a and the left bead 8b. By this turning up, a first main portion 44, a first right turn-up portion 46, and a first left turn-up portion 48 are formed in the first ply 40. The first main portion 44 extends from the right bead 8a to the left bead 8b. The first right turn-up portion 46 extends from the right bead 8a to the end E1a. The end E1a of the first right turn-up portion 46 is located to the left of the equatorial plane CL. In other words, the first right turn-up portion 46 straddles the equatorial plane CL. The first left turn-up portion 48 extends from the left bead 8b to the end E1b. The end E1b of the first left turn-up portion 48 is located to the right of the equatorial plane CL. In other words, the first left turn-up portion 48 straddles the equatorial plane CL. In the first ply 40, the first right turned-up portion 46 and the first left turned-up portion 48 overlap each other in the radial direction. In other words, the first ply 40 has a crown-overlap structure.

[0059] The second ply 42 is folded back at the right bead 8a and the left bead 8b. By this folding back, the second main portion 50, the second right turn-up portion 52, and the second left turn-up portion 54 are formed in the second ply 42. The second main portion 50 extends from the right bead 8a to the left bead 8b. The second right turn-up portion 52 extends from the right bead 8a to the end E2a. The end E2a of the second right turn-up portion 52 is located to the left of the equatorial plane CL. In other words, the second right turn-up portion 52 straddles the equatorial plane CL. The second left turn-up portion 54 extends from the left bead 8b to the end E2b. The end E2b of the second left turn-up portion 54 is located to the right of the equatorial plane CL. In other words, the second left turn-up portion 54 straddles the equatorial plane CL. In the second ply 42, the second right turned-up portion 52 and the second left turned-up portion 54 overlap each other in the radial direction. In other words, the second ply 42 has a crown-overlap structure.

[0060] In the carcass 38, on the equatorial plane CL, from the inside to the outside in the radial direction, First main portion 44, A second main portion 50, A second right folded portion 52; A first right folded portion 46; Second left fold 54 and First left fold 48 are arranged in this order. In this carcass 38, peeling at each end can be suppressed.

[0061] Fig. 10 is an exploded perspective view showing an enlarged portion of the carcass 38 of Fig. 9. Fig. 10 shows the vicinity of the equatorial plane CL of the carcass 38. As described above, in this carcass 38, the first main portion 44 is present at the innermost position in the radial direction. The inclination angle of the cords of this first main portion 44 is "positive (P)" (see Fig. 3). The second main portion 50 is present outside this first main portion 44. The inclination angle of the cords of this second main portion 50 is "negative (N)" (see Fig. 5).

[0062] A second right turned-up portion 52 exists on the outer side of the second main portion 50. The second right turned-up portion 52 is formed by turning up the second ply 42 at the right bead 8a, and therefore the inclination direction of the cords of this second right turned-up portion 52 is opposite to the inclination direction of the cords of the second main portion 50. The inclination angle of the cords of this second right turned-up portion 52 is "positive".

[0063] The first right turned-up portion 46 exists on the outer side of the second right turned-up portion 52. The first right turned-up portion 46 is formed by turning up the first ply 40 at the right bead 8a, and therefore the inclination direction of the cords of this first right turned-up portion 46 is opposite to the inclination direction of the cords of the first main portion 44. The inclination angle of the cords of this first right turned-up portion 46 is "negative".

[0064] A second left turned-up portion 54 exists on the outer side of the first right turned-up portion 46. The second left turned-up portion 54 is formed by turning up the second ply 42 at the left bead 8b, and therefore the inclination direction of the cords of this second left turned-up portion 54 is opposite to the inclination direction of the cords of the second main portion 50. The inclination angle of the cords of this second left turned-up portion 54 is "positive".

[0065] The first left turned-up portion 48 exists on the outer side of the second left turned-up portion 54. The first left turned-up portion 48 is formed by turning up the first ply 40 at the left bead 8b, and therefore the inclination direction of the cords of this first left turned-up portion 48 is opposite to the inclination direction of the cords of the first main portion 44. The inclination angle of the cords of this first left turned-up portion 48 is "negative".

[0066] In the carcass 38, on the equatorial plane CL, from the inside to the outside in the radial direction, Layer 44, where the inclination angle of the cord is "positive"; Layer 50, where the inclination angle of the cord is "negative"; Layer 52, where the inclination angle of the cord is "positive"; Layer 46, where the inclination angle of the cord is "negative"; Layer 54 where the cord inclination angle is "positive" and Layer 48, where the cord inclination angle is "negative" are arranged in this order. The total number of layers is 6. The number of layers with a "positive" cord inclination angle is 3. The number of layers with a "negative" cord inclination angle is 3. The number of layers with a "negative" cord inclination angle is the same as the number of layers with a "positive" cord inclination angle. A plurality of layers with a "positive" cord inclination angle and a plurality of layers with a "negative" cord inclination angle are arranged alternately. This carcass 38 can contribute to uniformity. In a tire having this carcass 38, uneven wear can be suppressed.

[0067] In respect of durability, the distance between the end E1a and the end E2a is preferably equal to or greater than 10 mm, more preferably equal to or greater than 15 mm, and particularly preferably equal to or greater than 18 mm. This distance is preferably equal to or less than 40 mm.

[0068] In respect of durability, the distance between the end E1b and the end E2b is preferably equal to or greater than 10 mm, more preferably equal to or greater than 15 mm, and particularly preferably equal to or greater than 18 mm. This distance is preferably equal to or less than 40 mm.

[0069] The ratio of the height of each end from the baseline BL to the height Ht of the tread end (see FIG. 1) is preferably 70% or more, more preferably 75% or more, and particularly preferably 80% or more. This ratio is preferably 90% or less.

[0070] The ratio of the distance from the equatorial plane CL of each end to the half width Wt / 2 of the tread (see FIG. 1) is preferably equal to or greater than 40%, more preferably equal to or greater than 50%, and particularly preferably equal to or greater than 55%. This ratio is preferably equal to or less than 90%.

[0071] The carcass 38 may have a shape that is a mirror image of the shape shown in Fig. 9 with respect to the equatorial plane CL. In this carcass 38, the following is true from the inside to the outside in the radial direction on the equatorial plane CL: First main part, Second main part, Second left fold, First left fold, Second right fold and First right fold In this carcass 38, peeling at each end can be suppressed. EXAMPLES

[0072] The effects of the present invention will be clarified by the following examples, but the present invention should not be construed as being limited based on the description of these examples.

[0073] [Example 1] A tire for a forklift truck shown in FIG. 1-8 was manufactured. The size of this tire was "7.00-12 12PR PL". The carcass of this tire had a first ply and a second ply. The first ply had a crown-overlap structure, and the second ply also had a crown-overlap structure. The number of plies was 2, and the number of layers at the equatorial plane CL was 6. The inclination angle of the cords in the main part of the first ply was +30°. The inclination angle of the cords in the main part of the second ply was -30°. In this tire carcass, the ratio of the height Hmin at the end where the height from the baseline BL is the smallest to the height Ht of the tread end was 75%. The ratio of the distance Wmin at the end where the distance from the equatorial plane CL is the smallest to the half width Wt / 2 of the tread was 55%.

[0074] [Example 2-4] Tires of Examples 2-4 were obtained in the same manner as in Example 1, except that the positions of the ends of the plies were changed and the ratios (Hmin / Ht) and (Wmin / (Wt / 2)) were set as shown in Table 1 below.

[0075] [Examples 5 and 6] Tires of Examples 5 and 6 were obtained in the same manner as in Example 1, except that the position of the end of the ply was changed and the ratio (Hmin / Ht), ratio (Wmin / (Wt / 2)), distance La and distance Lb were set as shown in Table 2 below.

[0076] [Example 7] A tire of Example 7 was obtained in the same manner as in Example 1, except that the inclination angle of the cords of the second ply was set to +30°.

[0077] [Example 8] A tire of Example 8 was obtained in the same manner as in Example 1, except that a carcass having the structure shown in FIG.

[0078] [Comparative Example 1] Except for forming a carcass from six plies, a tire of Comparative Example 1 was obtained in the same manner as in Example 1. Each ply did not have a crown-overlap structure.

[0079] [Durability] The tire was mounted on a rim and filled with air so that the internal pressure of the tire was a normal value. The tire was then mounted on a drum-type running test machine and run under the following conditions. Speed: 15km / h Load: 2260kgf Environmental temperature: 25-30℃ The distance traveled until damage occurred to the side of the tire was measured. The results are shown as an index in Tables 1 and 2 below. The higher the value, the greater the distance traveled.

[0080] [cost] The amount of rubber in the tire was calculated and then the reciprocal was calculated. The results are shown as an index in Tables 1 and 2 below. The higher the value, the less rubber there is.

[0081] [Total points] The durability and cost ratings were added together, and the results are shown in Tables 1 and 2 below. The higher the value, the better the overall rating.

[0082] [Uneven wear] During the above-mentioned durability test, the tire tread was visually observed. The presence or absence of uneven wear was judged. The results are shown in Tables 1 and 2 below.

[0083] [Table 1]

[0084] [Table 2]

[0085] As shown in Tables 1 and 2, the tires according to the respective examples have an excellent balance between low cost and durability. From these evaluation results, the superiority of the present invention is clear. [Industrial Applicability]

[0086] The pneumatic tire according to the present invention can be mounted on various vehicles. [Explanation of symbols]

[0087] 2. Pneumatic tires 4. Tread 6. Sidewall 8...Bead 8a Right bead 8b... Left bead 10. Carcass 18. First Ply 20...Second ply 22...First main section 24 First right fold 26 First left fold 28...Second main section 30 Second right fold 32 Second left fold 34...Code 36 Topping rubber 38...Carcass 40···First ply 42...Second ply 44 First main section 46 First right fold 48 First left fold 50...Second main section 52 Second right fold 54 Second left fold

Claims

1. A pneumatic tire having a right bead, a left bead, a carcass, and a tread, the carcass having a first ply and a second ply, The first ply includes a plurality of cords arranged in parallel and inclined with respect to a circumferential direction, The second ply includes a plurality of cords arranged in parallel and inclined with respect to a circumferential direction, The first ply is folded back at the right bead and the left bead, thereby forming a first main portion, a first right turn-up portion, and a first left turn-up portion in the first ply, The second ply is folded back at the right bead and the left bead, thereby forming a second main portion, a second right folded back portion and a second left folded back portion in the second ply, an end of the first right turned-up portion is located to the left of an equatorial plane of the tire, an end of the first left folded-back portion is located to the right of the equatorial plane, an end of the second right folded-back portion is located to the left of the equatorial plane, an end of the second left folded-back portion is located to the right of the equatorial plane, On the equatorial plane, from the inner side to the outer side in the radial direction of the tire, The first main part, The second main part, The second right folded portion, The second left folded portion, The first right folded part and The first left folded part But here are the pneumatic tires, lined up in this order.

2. A pneumatic tire having a right bead, a left bead, a carcass, and a tread, the carcass having a first ply and a second ply, The first ply includes a plurality of cords arranged in parallel and inclined with respect to a circumferential direction, The second ply includes a plurality of cords arranged in parallel and inclined with respect to a circumferential direction, The first ply is folded back at the right bead and the left bead, thereby forming a first main portion, a first right turn-up portion, and a first left turn-up portion in the first ply, The second ply is folded back at the right bead and the left bead, thereby forming a second main portion, a second right folded back portion and a second left folded back portion in the second ply, an end of the first right turned-up portion is located to the left of an equatorial plane of the tire, an end of the first left folded-back portion is located to the right of the equatorial plane, an end of the second right folded-back portion is located to the left of the equatorial plane, an end of the second left folded-back portion is located to the right of the equatorial plane, On the equatorial plane, from the inner side to the outer side in the radial direction of the tire, The first main part, The second main part, The second left folded portion, The second right folded portion, The first left folded part and The first right folded part But here are the pneumatic tires, lined up in this order.

3. 3. The tire according to claim 1, wherein a direction of inclination of the cords in the second main portion with respect to the equator plane is opposite to a direction of inclination of the cords in the first main portion with respect to the equator plane.

4. an end of the first right folded portion and an end of the second right folded portion are spaced apart from each other, 4. The tire according to claim 1, wherein an end of the first left turned-up portion and an end of the second left turned-up portion are spaced apart from each other.

5. The distance between an end of the first right folded portion and an end of the second right folded portion is 10 mm or more; The tire according to claim 4 , wherein a distance between an end of the first left turned-up portion and an end of the second left turned-up portion is 10 mm or more.

6. a ratio of a height of an end of the first right folded-back portion to a height of the tire is 70% or more; a ratio of a height of an end of the first left folded-back portion to a height of the tire is 70% or more; a ratio of a height of an end of the second right folded-back portion to a height of the tire is 70% or more; The pneumatic tire according to claim 1 , wherein a ratio of a height of the end of the second left folded-back portion to a height of the tire is equal to or greater than 70%.

7. a ratio of a distance from the equatorial plane to an end of the first right turn-up portion to a half width of the tread is 40% or more; a ratio of a distance from the equatorial plane to an end of the first left turn-up portion to a half width of the tread is 40% or more; a ratio of a distance from the equatorial plane to an end of the second right turn-up portion to a half width of the tread is 40% or more; 7. The pneumatic tire according to claim 1, wherein a ratio of a distance from the equatorial plane to an end of the second left turned-up portion to a half width of the tread is 40% or more.

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