Pneumatic tire

Abstract

To provide a pneumatic tire which can achieve weight saving while keeping durability.SOLUTION: A pneumatic tire 1 comprises a carcass 6, a belt layer 7, and a reinforcement rubber layer 10. A folded section 6b of a carcass ply 6A includes: a first part 11 which is positioned between a body part 6a and the belt layer 7; a second part 12 which is arranged at an outer side of a rim flange Rf of a normal rim R in a tire radial direction adjacent to the reinforcement rubber layer 10 in a tire axial direction; and a third part 13 which is arranged between the first part 11 and the second part 12. Length Lc of the third part 13 is 0.8 to 1.4 times the sum (La+Lb) of length La of the first part 11 and length Lb of the second part 12.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] The following Patent Document 1 describes a tire having a carcass composed of one carcass ply. The carcass ply has a ply body and a pair of turned-up portions. The ends of the turned-up portions are located axially inward from the ground-contact end of the tread. Such a tire is designed to be lightweight. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2022-100772 A Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, there has been a demand for reducing the weight of pneumatic tires while maintaining their durability.

[0005] The present invention has been devised in view of the above circumstances, and has as its main object to provide a pneumatic tire that can be made lighter while maintaining durability. [Means for solving the problem]

[0006] The present invention is a pneumatic tire including a tread portion, a pair of sidewall portions, a pair of bead portions each having a bead core, a carcass extending between the pair of bead portions, a belt layer disposed on the outer side of the carcass in the tire radial direction, and a reinforcing rubber layer provided on each of the pair of bead portions, wherein the carcass includes a main body portion extending between the bead cores of the pair of bead portions, and a pair of foldback portions having outer ends folded back around each of the bead cores from the inner side to the outer side in the tire axial direction and extending outward in the tire radial direction. and a ridge portion, and in a tire meridian cross section in a normal state in which the tire is mounted on a normal rim and inflated to a normal internal pressure and is unloaded, each of the pair of folded-up portions includes a first portion located between the main body portion and the belt layer, a second portion that is radially outward of a rim flange of the normal rim and adjacent to the reinforcing rubber layer in the tire axial direction, and a third portion between the first portion and the second portion, and a length of the third portion is 0.8 to 1.4 times the sum of the length of the first portion and the length of the second portion. Effect of the Invention

[0007] By employing the above configuration, the pneumatic tire of the present invention can be made lighter while maintaining durability. [Brief description of the drawings]

[0008] [Figure 1] 1 is a tire meridian cross-sectional view of the right half of one embodiment of a pneumatic tire of the present invention. FIG. [Diagram 2] FIG. [Diagram 3] FIG. 2 is an enlarged view of a bead portion in FIG. [Figure 4] FIG. 4 is a cross-sectional view taken along line AA in FIG. [Diagram 5] FIG. 2 is an enlarged view of a bead portion in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In order to facilitate understanding of the present invention, the drawings include exaggerated representations and representations different from the dimensional ratios of the actual structures. In addition, when there are multiple embodiments, the same or common elements are designated by the same reference numerals throughout the specification, and duplicated explanations are omitted.

[0010] FIG. 1 is a tire meridian cross-sectional view of the right half including the tire rotation axis (not shown) of one embodiment of a pneumatic tire (hereinafter sometimes simply referred to as "tire") 1 of the present invention. FIG. 1 shows a tire 1 for passenger cars as a preferred embodiment. The present invention is particularly suitable for tires mounted on commercial vehicles (e.g., vans) that are expected to be subjected to high loads. However, the present invention may also be applied to tires 1 for small trucks and heavy loads, for example.

[0011] In this specification, unless otherwise specified, the dimensions of each part of the tire 1 are measured in a normal state. The "normal state" refers to a state in which the tire 1 is mounted on a normal rim (hereinafter sometimes simply referred to as "rim") R, inflated to the normal internal pressure, and no load is applied.

[0012] "Genuine rim R" is the rim that is specified for each tire by the standard system that includes the standard on which the tire is based. For example, in the case of JATMA, it is called "standard rim", in the case of TRA, it is called "Design Rim", and in the case of ETRTO, it is called "Measuring Rim".

[0013] "Normal internal pressure" is the air pressure set for each tire by each standard in the standard system on which the tire is based. In the case of JATMA, it is the "maximum air pressure." In the case of TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES." In the case of ETRTO, it is the "INFLATION PRESSURE."

[0014] The tire 1 of this embodiment includes a tread portion 2, a pair of sidewall portions 3, and a pair of bead portions 4 each having a bead core 5. Only one of the sidewall portions 3 and one of the bead portions 4 is shown in Fig. 1. In this embodiment, the tire 1 also includes a carcass 6 extending between the pair of bead portions 4, a belt layer 7 disposed on the outer side of the carcass 6 in the tire radial direction, and a reinforcing rubber layer 10 provided on each of the pair of bead portions 4.

[0015] The carcass 6 is a carcass ply 6A including a main portion 6a extending between the bead cores 5 of the pair of bead portions 4, and a pair of turn-up portions 6b having outer ends 6e that are turned back from the inside to the outside in the tire axial direction around each bead core 5 and extend outward in the tire radial direction. As described above, the carcass 6 of this embodiment is formed of a single carcass ply 6A, and therefore, the weight can be reduced.

[0016] In a tire meridian cross section in a normal state, each of the pair of turned-up portions 6b includes a first portion 11, a second portion 12, and a third portion 13. The first portion 11 is located between the main body portion 6a and the belt layer 7. The second portion 12 is adjacent to the reinforcing rubber layer 10 in the tire axial direction, on the outer side of the rim flange Rf of the rim R in the tire radial direction. The third portion 13 is located between the first portion 11 and the second portion 12. The first portion 11 and the second portion 12 are supported by the belt layer 7 and the reinforcing rubber layer 10, and the tension acting on the turned-up portion 6b is alleviated, thereby maintaining durability. In addition, the reinforcing rubber layer 10 keeps the carcass ply 6A away from the rim flange Rf, thereby suppressing damage to the carcass ply 6A, thereby maintaining even higher durability.

[0017] In addition, when a rubber material (for example, sidewall rubber 3G) is arranged between the belt layer 7 and the turned-up portion 6b, the first portion 11 includes an area where the turned-up portion 6b abuts against the belt layer 7 when the belt layer 7 is folded assuming that the sidewall rubber 3G is not present. In addition, when the belt layer 7 is formed of a plurality of belt plies, the first portion 11 is specified by the belt ply arranged on the innermost side in the tire radial direction (in the present embodiment, the inner belt ply 7A). In addition, the second portion 12 is formed on the outer side in the tire radial direction of the tire than the outer end e1 in the tire radial direction of the rim flange Rf. For convenience, the first portion 11 and the second portion 12 are shown by hatching in FIG. 1.

[0018] FIG. 2 is a development view of the carcass ply 6A. As shown in FIG. 2, the length Lc of the third portion 13 is preferably 0.8 times or more, more preferably 0.9 times or more, more preferably 1.4 times or less, and even more preferably 1.3 times or less of the sum (La+Lb) of the length La of the first portion 11 and the length Lb of the second portion 12. Since the length Lc of the third portion 13 is 0.8 times or more of the sum (La+Lb), the tire 1 is made lighter. Furthermore, since the length Lc of the third portion 13 is 1.4 times or less of the sum (La+Lb), the effect of relaxing the tension by the first portion 11 and the second portion 12 is maintained at a high level. Therefore, the tire 1 of the present invention can be made lighter while maintaining durability. This effect is particularly effective for the pneumatic tire 1 to be mounted on commercial vehicles and small trucks that are expected to be subjected to high loads.

[0019] Generally, when the tire 1 is running, a relatively large tension acts on the carcass ply 6A of the bead portion 4. For this reason, it is desirable that the length Lb of the second portion 12 is greater than the length La of the first portion 11. Although not particularly limited, the length Lb of the second portion 12 is desirably 1.05 times or more of the length La of the first portion 11, more desirably 1.08 times or more, desirably 1.18 times or less, and more desirably 1.15 times or less.

[0020] As shown in Fig. 1, in this embodiment, the belt layer 7 is composed of two belt plies 7A and 7B, one inside and one outside in the tire radial direction. For example, the inner belt ply 7A terminates further outward in the tire axial direction than the outer belt ply 7B. In this embodiment, each of the belt plies 7A and 7B has a highly elastic belt cord such as a steel cord inclined at an angle of 15 to 40 degrees with respect to the tire equator C, and a topping rubber (not shown) that covers the belt cord. In this way, each of the belt plies 7A and 7B can be appropriately selected from known ones.

[0021] 2, the carcass ply 6A includes a plurality of carcass cords 6c and a topping rubber Gt that covers the carcass cords 6c. Well-known materials may be appropriately used for the carcass cords 6c and the topping rubber Gt.

[0022] The length Wa (shown in FIG. 1) in the tire axial direction between the outer ends 6e of the pair of turned-up portions 6b is preferably 0.10 times or more, more preferably 0.15 times or more, more preferably 0.30 times or less, and even more preferably 0.25 times or less, of the length L1 of the main body portion 6a. Since the length Wa between the outer ends 6e is 0.10 times or more of the length L1 of the main body portion 6a, the tire 1 is kept highly lightweight. Since the length Wa between the outer ends 6e is 0.30 times or less of the length L1 of the main body portion 6a, the effect of supporting the turned-up portion 6b is highly exhibited. The length L1 of the main body portion 6a is the length between the positions 6i (shown in FIG. 1) that are the innermost in the tire radial direction of the carcass ply 6A. When a plurality of positions 6i that are the innermost in the tire radial direction are formed, the length L1 is the length at the position that is the innermost in the tire axial direction.

[0023] As shown in Fig. 1, the bead core 5 of this embodiment is formed in a rectangular shape in a tire meridian cross section. The bead core 5 includes an outer surface 5a in the tire radial direction, an inner surface 5b in the tire radial direction, an inner surface 5c in the tire axial direction, and an outer surface 5d in the tire axial direction. The inner surface 5c and the outer surface 5d are connected to the outer surface 5a and the inner surface 5b. The bead core 5 employs a well-known structure formed by winding a non-stretchable bead wire, for example.

[0024] In this embodiment, the outer end 10e of the reinforcing rubber layer 10 in the tire radial direction is preferably located outside the outer end e1 of the rim flange Rf in the tire radial direction. Such a reinforcing rubber layer 10 can suppress the bending of the bead portion 4 that occurs during running, and further suppress damage to the carcass ply 6A. In addition, by suppressing the bending of the bead portion 4, it is possible to suppress peeling of each tire component. Although not particularly limited, the distance H1 in the tire radial direction between the outer end 10e of the reinforcing rubber layer 10 and the outer end e1 of the rim flange Rf is preferably 15% or more of the tire cross-sectional height H, more preferably 20% or more, more preferably 35% or less, and even more preferably 30% or less. In this specification, the "tire cross-sectional height H" is the tire radial distance from the bead base line BL to the outermost position in the tire radial direction. In addition, the "bead base line BL" is a tire axial line passing through the rim diameter (see JATMA) position determined by the standard on which the tire 1 is based.

[0025] Fig. 3 is an enlarged view of the bead portion 4 in Fig. 1. As shown in Figs. 1 and 3, it is desirable that the inner end 10i in the tire radial direction of the reinforcing rubber layer 10 is located radially outward of the outer surface 5a in the tire radial direction of the bead core 5. Such a reinforcing rubber layer 10 suppresses an increase in the mass of the tire 1. Also, the inner end 10i of the reinforcing rubber layer 10 is located, for example, radially inward of the outer end e1 of the rim flange Rf. This maintains high rigidity of the bead portion 4.

[0026] The reinforced rubber layer 10 is formed of, for example, a sheet-like rubber member. Such a reinforced rubber layer 10 increases the rigidity of the bead portion 4 uniformly in the tire radial direction, and suppresses an increase in the mass of the tire 1. The thickness (maximum thickness) t1 of the reinforced rubber layer 10 is preferably 0.5 to 3.0 mm. The complex elastic modulus E*c of the reinforced rubber layer 10 is preferably, for example, 15 MPa or more, more preferably 20 MPa or more, and more preferably 100 MPa or less, and even more preferably 80 MPa or less. This allows the rigidity of the bead portion 4 to be maintained high. In this specification, the complex elastic modulus E* is a value measured under the conditions shown below using a viscoelasticity spectrometer such as "Eplexer (registered trademark)" manufactured by GABO Co., Ltd. in accordance with JIS K6394. Initial strain: 10% Amplitude: ±2% Frequency: 10Hz Deformation mode: tension Temperature: 70℃

[0027] As shown in FIG. 1, the tire 1 of this embodiment further includes a bead apex rubber 8, a reinforcing layer 15, a sidewall rubber 3G, and a clinch rubber 4G. The bead apex rubber 8 is provided, for example, on each of the pair of bead portions 4, and extends from the outer surface 5a of the bead core 5 in the tire radial direction to the outside in the tire radial direction. The reinforcing layer 15 is provided, for example, on each of the pair of bead portions 4, and is disposed between the bead core 5 and the carcass ply 6A. In this embodiment, the sidewall rubber 3G is disposed on the outside in the tire axial direction from the turn-up portion 6b, and is adjacent to the third portion 13. The clinch rubber 4G is, for example, located on the outside of the reinforcing rubber layer 10 in the tire axial direction, and forms the outer surface of the tire 1 that abuts against the rim R.

[0028] 3, the reinforcing layer 15 of this embodiment includes an inner portion 15A and an outer portion 15B. The inner portion 15A is adjacent to, for example, the inner surface 5c of the bead core 5. The outer portion 15B is connected to the inner portion 15A and is folded back around the bead core 5 from the inner side in the tire axial direction to the outer side, extending outward in the tire radial direction.

[0029] The outer end 15e of the inner portion 15A and the outer end 15i of the outer portion 15B are located radially outward of the outer surface 5a of the bead core 5. The outer end 15e of the inner portion 15A and the outer end 15i of the outer portion 15B are located radially outward of the inner end 10i of the reinforcing rubber layer 10. Such a reinforcing layer 15 greatly reduces the possibility of contact between the bead core 5 and the carcass ply 6A. This reduces the risk of the carcass cord 6c of the carcass ply 6A being cut, improving durability. The outer end 15e of the inner portion 15A and the outer end 15i of the outer portion 15B are located radially inward of the outer end e1 of the rim flange Rf.

[0030] The radially outer end 15e of the inner portion 15A is at the same position in the tire radial direction as the radially outer end 15i of the outer portion 15B. Such a reinforcing layer 15 suppresses movement of the bead core 5 and rotation of the bead core 5 about the illustrated center, and further suppresses contact between the carcass ply 6A and the bead core 5. In this specification, the "same position" includes not only a case where the radially outer end Lt between the outer ends 15e and 15i is 0 mm, but also a case where Lt is 3 mm or less.

[0031] The distance Lp in the tire radial direction between the outer end 15i of the outer portion 15B and the outer surface 5a of the bead core 5 is preferably 30% or more of the height H2 (shown in FIG. 5) of the bead apex rubber 8 in the tire radial direction, more preferably 35% or more, more preferably 50% or less, and even more preferably 45% or less. Since the distance Lp is 30% or more of the height H2 of the bead apex rubber 8, contact between the carcass ply 6A and the bead core 5 can be effectively suppressed. Since the distance Lp is 50% or less of the height H2 of the bead apex rubber 8, the adhesive strength between the bead apex rubber 8 and the carcass ply 6A is maintained high, and damage due to peeling is suppressed. The height H2 of the bead apex rubber 8 is the length in the tire radial direction between the outer end 8e of the bead apex rubber 8 and the outer surface 5a of the bead core 5.

[0032] Fig. 4 is a cross-sectional view taken along line AA in Fig. 3. As shown in Fig. 4, in this embodiment, the reinforcing layer 15 is a reinforcing ply 15p including a plurality of organic fiber cords 15c and a first rubber G1 that covers the organic fiber cords 15c. The organic fiber cords 15c are made of, for example, polyester fiber, nylon fiber, rayon fiber, vinylon fiber, aramid fiber, or polyurethane fiber.

[0033] The product (Ca×E*1) of the cord density Ca of the carcass ply 6A and the complex modulus E*1 of the topping rubber Gt is preferably greater than the product (Cb×E*2) of the cord density Cb of the reinforcing ply 15p and the complex modulus E*2 of the first rubber G1. This allows the reinforcing layer 15 to be precisely arranged along the inner surface 5c and the inner surface 5b of the bead core 5, and also prevents damage to the carcass ply 6A. The product (Ca×E*1) is preferably, for example, 90,000 to 110,000 (pieces·MPa). The product (Cb×E*2) is preferably, for example, 15,000 to 25,000 (pieces·MPa). In this specification, the "cord density" refers to the number of each cord included in each ply per 50 mm of ply width.

[0034] Fig. 5 is an enlarged view of the bead portion 4 in Fig. 1. As shown in Fig. 5, the bead apex rubber 8 is inclined outward in the tire axial direction toward the outer side in the tire radial direction. As the bead apex rubber 8 of this embodiment, a well-known one can be appropriately adopted.

[0035] The outer end 8e of the bead apex rubber 8 in the tire radial direction is located, for example, outside the outer end e1 of the rim flange Rf in the tire radial direction. This further suppresses the bending of the bead portion 4 during running, and for example, prevents peeling between the carcass ply 6A and the reinforcing rubber layer 10 and between the main portion 6a and the folded-up portion 6b, thereby improving durability. In this embodiment, the bead apex rubber 8 extends along the inner and outer sides of the outer end e1 of the rim flange Rf in the tire radial direction.

[0036] The height H2 of the bead apex rubber 8 in the tire radial direction is preferably 30 mm or less, and more preferably 28 mm or less. Since the height H2 of the bead apex rubber 8 is 30 mm or less, the outer end 8e of the bead apex rubber 8 and the bending point of the bead portion 4 during running are prevented from coming too close to each other, so that durability is maintained at a high level. Although not particularly limited, the height H2 of the bead apex rubber 8 is preferably 5 mm or more, and more preferably 10 mm or more.

[0037] In this embodiment, the radially inner end 3i of the sidewall rubber 3G is located radially inward of the outer end e1 of the rim flange Rf. The radially outer end 3e (shown in FIG. 1) of the sidewall rubber 3G is located, for example, between the inner belt ply 7A and the turned-up portion 6b.

[0038] The thickness (maximum thickness) t3 (shown in FIG. 1) of the sidewall rubber 3G is preferably 2.0 mm or more, more preferably 2.5 mm or more, more preferably 6.0 mm or less, and even more preferably 5.0 mm or less. Since the thickness t3 of the sidewall rubber 3G is 2.0 mm or more, the rigidity of the sidewall portion 3 can be increased. Since the thickness t3 of the sidewall rubber 3G is 6.0 mm or less, the tire 1 can be kept lightweight. The thickness t3 of the sidewall rubber 3G is the length in the normal direction on the outer surface in the axial direction of the tire of the turned-up portion 6b of the carcass ply 6A.

[0039] In this embodiment, the outer end 4e of the clinch rubber 4G in the tire radial direction is located outside in the tire radial direction of the outer end 8e of the bead apex rubber 8. The clinch rubber 4G is adjacent to the outer side surface 5d of the bead core 5 and extends radially inward of the inner surface 5b.

[0040] The complex modulus E*5 of the bead apex rubber 8 is preferably 15 MPa or more, more preferably 20 MPa or more, more preferably 100 MPa or less, and more preferably 80 MPa or less. The complex modulus E*6 of the sidewall rubber 3G is preferably 3 MPa or more, more preferably 5 MPa or more, more preferably 20 MPa or less, and more preferably 15 MPa or less. The complex modulus E*7 of the clinch rubber 4G is preferably 5 MPa or more, more preferably 8 MPa or more, more preferably 20 MPa or less, and more preferably 15 MPa or less.

[0041] The bead toe Bt is the axially innermost point of the tire that contacts the rim R. The bead heel Bh is the point that contacts the rim R and intersects with the bead baseline BL. In each of the pair of bead portions 4, the length Wb in the tire axial direction between the bead toe Bt and the bead heel Bh is preferably 16 mm or less. Such a length Wb improves the rim assembly performance when the rim R and the tire 1 are fitted together. To ensure stability during running, the length Wb is preferably 12 mm or more.

[0042] Although a particularly preferred embodiment of the present invention has been described in detail above, the present invention is not limited to the illustrated embodiment and can be modified and carried out in various forms. EXAMPLES

[0043] A pneumatic tire for small trucks with a size of 205 / 85R16LT and the basic structure shown in Fig. 1 was prototyped based on the specifications in Table 1. It was then tested for weight reduction and durability. The test method was as follows.

[0044] <Lightweight> The mass of each test tire was measured. The results were expressed as an index, with the reciprocal of the mass of Comparative Example 3 taken as 100. The larger the value, the smaller the mass of the tire and the better the result.

[0045] <Durability> Each test tire was run on a drum tester under the following conditions, and the running distance when carcass cord damage or peeling damage occurred was measured. Carcass cord damage refers to damage caused by the carcass cord breaking around the bead core. Peeling damage refers to peeling between the carcass ply and the adjacent constituent material, and peeling between the carcass plies themselves. Evaluation was based on the running distance when either carcass cord damage or peeling damage occurred. The results were expressed as an index, with the running distance of Comparative Example 1 being set at 60. A value of 90 or more is a pass. Internal pressure: 600kPa Load: 19.84kN Traveling speed: 80km / h The test results are shown in Tables 1 and 2. In addition, "2 plies" in Table 1 is an example in which two carcass plies are arranged and the outer ends 6e of both turn-up portions are located at the maximum tire width position. In addition, "A" in Tables 1 and 2 means "8e>e1>15e, 15i", and "B" means "e1>8e>15e, 15i". Furthermore, in Tables 1 and 2, "C" means "(Ca×E*1)>(Cb×E*2)" and "D" means "(Ca×E*1)<(Cb×E*2)". In addition, in Tables 1 and 2, "Yes" means that the reinforcing layer was formed with a reinforcing ply, and "Yes*" means that the reinforcing layer was formed only with rubber. Furthermore, Comparative Example 1 is an example in which the height H2 of the bead apex rubber in the radial direction of the tire is the same height as that in Figure 1, and Comparative Example 2 is an example in which the height H2 of the bead apex rubber is set so that the durability performance is 100.

[0046] [Table 1]

[0047] [Table 2]

[0048] As shown in the table, it can be seen that the tires of the examples have improved durability while maintaining a lighter weight compared to the tires of the comparative examples.

[0049] [Note] The present invention includes the following aspects.

[0050] [Invention 1] A pneumatic tire, A tread portion; A pair of sidewall portions; A pair of bead portions each having a bead core; a carcass extending between the pair of bead portions; A belt layer disposed on an outer side of the carcass in the tire radial direction; a reinforcing rubber layer provided on each of the pair of bead portions, the carcass is a carcass ply including a main body portion extending between the bead cores of the pair of bead portions, and a pair of turn-up portions having outer ends turned back around the respective bead cores from the inside to the outside in the tire axial direction and extending outward in the tire radial direction, When the tire is mounted on a standard rim, inflated to the standard internal pressure, and in a standard unloaded condition, the tire meridian cross section is as follows: Each of the pair of folded-up portions includes a first portion located between the main body portion and the belt layer, a second portion adjacent to the reinforcing rubber layer in the tire axial direction outside a rim flange of the regular rim in the tire radial direction, and a third portion between the first portion and the second portion, The length of the third portion is 0.8 to 1.4 times the sum of the length of the first portion and the length of the second portion. Pneumatic tires. [Invention 2] The pneumatic tire according to aspect 1, wherein the length in the tire axial direction between the outer ends of the pair of folded-back portions is 0.1 to 0.3 times the length of the main body portion. [Invention 3] The pneumatic tire according to claim 1 or 2, wherein a reinforcing layer is provided between the bead core and the carcass ply in each of the pair of bead portions. [Invention 4] Each of the pair of bead portions is provided with a bead apex rubber extending from an outer surface of the bead core in the tire radial direction to an outer side in the tire radial direction, In the normal state, A pneumatic tire according to present invention 3, wherein the radially outer end of the bead apex rubber and the radially outer end of the reinforcing rubber layer are positioned radially outward of the radially outer end of the rim flange of the regular rim. [Invention 5] the reinforcing layer includes an inner portion adjacent to an inner surface of the bead core in the tire axial direction, and an outer portion connected to the inner portion, folded back around the bead core from the inner side in the tire axial direction to the outer side, and extending outward in the tire radial direction, The pneumatic tire according to invention 3 or 4, wherein an outer end in the tire radial direction of the inner portion is at the same position in the tire radial direction as an outer end in the tire radial direction of the outer portion. [Invention 6] A pneumatic tire as described in invention 5, wherein the radially outer end of the inner portion and the radially outer end of the outer portion are positioned radially outward of the radially inner end of the reinforcing rubber layer. [Invention 7] The pneumatic tire according to any one of claims 3 to 6, wherein the reinforcing layer is a reinforcing ply including a plurality of organic fiber cords and a first rubber covering the organic fiber cords. [Invention 8] The pneumatic tire according to any one of claims 1 to 7, wherein an inner end in the tire radial direction of the reinforcing rubber layer is located outer in the tire radial direction than an outer surface in the tire radial direction of the bead core. [The present invention 9] The carcass ply includes a plurality of carcass cords and a topping rubber covering the carcass cords, The pneumatic tire according to invention 7, wherein the product of the cord density of the carcass ply and the complex modulus of the topping rubber is greater than the product of the cord density of the reinforcing ply and the complex modulus of the first rubber. [The present invention 10] 10. The pneumatic tire according to any one of claims 1 to 9, wherein in each of the pair of bead portions, the length in the tire axial direction between the bead toe and the bead heel is 16 mm or less. [The present invention 11] a sidewall rubber adjacent to an outer side of the third portion in the tire axial direction, 11. The pneumatic tire according to any one of claims 1 to 10, wherein the sidewall rubber has a thickness of 2.0 to 6.0 mm. [Explanation of symbols]

[0051] 1. Pneumatic tires 6. Carcass 6A Carcass Ply 6a Main body 6b Folded part 7 Belt layer 10 Reinforcement rubber layer 11 Part 1 12 Part 2 13 Part 3 La, Lb, Lc Length R Genuine rim Rf rim flange

Claims

1. A pneumatic tire, A tread portion; A pair of sidewall portions; A pair of bead portions each having a bead core; a carcass extending between the pair of bead portions; A belt layer disposed on an outer side of the carcass in the tire radial direction; a reinforcing rubber layer provided on each of the pair of bead portions, the carcass is a carcass ply including a main body portion extending between the bead cores of the pair of bead portions, and a pair of turn-up portions having outer ends turned back around the respective bead cores from the inside to the outside in the tire axial direction and extending outward in the tire radial direction, When the tire is mounted on a standard rim, inflated to the standard internal pressure, and in a standard unloaded condition, the tire meridian cross section is as follows: Each of the pair of folded-up portions includes a first portion located between the main body portion and the belt layer, a second portion adjacent to the reinforcing rubber layer in the tire axial direction and further outward in the tire radial direction than a rim flange of the regular rim, and a third portion between the first portion and the second portion, The length of the third portion is 0.8 to 1.4 times the sum of the length of the first portion and the length of the second portion. Pneumatic tires.

2. The pneumatic tire according to claim 1, wherein a length in the tire axial direction between the outer ends of each of the pair of folded-up portions is 0.1 to 0.3 times a length of the main body portion.

3. The pneumatic tire according to claim 2 , wherein each of the pair of bead portions includes a reinforcing layer provided between the bead core and the carcass ply.

4. Each of the pair of bead portions is provided with a bead apex rubber extending from an outer surface of the bead core in the tire radial direction to an outer side in the tire radial direction, In the normal state, 4. The pneumatic tire according to claim 3, wherein a radially outer end of the bead apex rubber and a radially outer end of the reinforcing rubber layer are positioned radially outward of a radially outer end of a rim flange of the regular rim.

5. the reinforcing layer includes an inner portion adjacent to an inner surface of the bead core in the tire axial direction, and an outer portion connected to the inner portion, folded back around the bead core from the inner side in the tire axial direction to the outer side, and extending outward in the tire radial direction, The pneumatic tire according to claim 3 or 4, wherein an outer end in the tire radial direction of the inner portion is located at the same position in the tire radial direction as an outer end in the tire radial direction of the outer portion.

6. 6. The pneumatic tire according to claim 5, wherein a radially outer end of the inner portion and a radially outer end of the outer portion are positioned radially outward of an inner end of the reinforcing rubber layer in the tire radial direction.

7. The pneumatic tire according to claim 3 , wherein the reinforcing layer is a reinforcing ply including a plurality of organic fiber cords and a first rubber covering the organic fiber cords.

8. The pneumatic tire according to claim 1 , wherein an inner end in a radial direction of the reinforcing rubber layer is located radially outward of an outer surface of the bead core in the tire radial direction.

9. The carcass ply includes a plurality of carcass cords and a topping rubber covering the carcass cords, The pneumatic tire according to claim 7 , wherein a product of a cord density of the carcass ply and a complex modulus of elasticity of the topping rubber is greater than a product of a cord density of the reinforcing ply and a complex modulus of elasticity of the first rubber.

10. 5. The pneumatic tire according to claim 1, wherein a length in the tire axial direction between a bead toe and a bead heel in each of the pair of bead portions is 16 mm or less.

11. a sidewall rubber adjacent to an outer side of the third portion in the tire axial direction, 5. The pneumatic tire according to claim 1, wherein the sidewall rubber has a thickness of 2.0 to 6.0 mm.

Images