JP2017013538A - Heavy duty tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heavy duty tire improving the durability of a bead portion.SOLUTION: A heavy duty tire has a carcass 6 made from a carcass ply 6A including a body portion 6a and a folded portion 6b. A bead portion 4 is provided with a first reinforcing portion 11 on the body portion 6a side, and a second reinforcing portion 12 on the folded portion 6b side. The first reinforcing portion 11 is composed of a first steel cord ply 21, and a second steel cord ply 22 with a generally U-shaped cross section. The second reinforcing portion 12 is composed of a first organic fiber cord ply 31 and a second organic fiber cord ply 32 covering an outer end on the folded portion 6b side of the second steel cord ply 22 from the outside in a tire axial direction.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a heavy duty tire with improved bead durability.

  For example, Patent Document 1 below proposes a heavy load tire in which a reinforcement portion is provided in a bead portion. The reinforcing portion of Patent Document 1 includes a first steel cord ply extending in the tire radial direction on the main body side of the carcass ply, and a second steel having a substantially U-shaped cross section wound around the bead core from the inner side to the outer side in the tire axial direction. It consists of a cord ply.

  However, in the tire of Patent Document 1, when the bead portion is bent and deformed outward in the tire axial direction, stress tends to concentrate on the end portion of the second steel cord ply, and as a result, damage such as separation occurs on the end portion. It was. Therefore, the conventional technology has room for further improvement in improving the durability of the bead portion.

JP 2012-106531 A

  The present invention has been devised in view of the actual situation as described above. The bead portion is based on providing the first reinforcing portion on the main body portion side of the carcass ply and the second reinforcing portion on the folded portion side. The main purpose is to provide a heavy duty tire with improved durability.

  The present invention is a carcass ply including a main body part that extends from a tread part through a sidewall part to a bead core of a bead part, and a folded part that is continuous with the main body part and that turns around the bead core from the inner side to the outer side in the tire axial direction. A heavy duty tire having a carcass, wherein the bead portion includes at least a first reinforcing portion extending in a tire radial direction on an inner side in a tire axial direction of the main body portion, and at least a portion of the folded portion tire. A second reinforcing portion extending in the tire radial direction on the outer side in the axial direction, and the first reinforcing portion includes at least one first steel cord ply extending in the tire radial direction along the inner side in the tire axial direction of the main body portion. The portion overlaps with the first steel cord ply, and is wound around the bead core from the inner side to the outer side in the tire axial direction. A second steel cord ply having a substantially U-shaped cross section having an outer end that terminates inward in the tire radial direction with respect to the outer end of the ridge portion, and the second reinforcing portion is the folded portion of the second steel cord ply It consists of the 1st organic fiber cord ply and the 2nd organic fiber cord ply which cover the said outer end of the side from the tire axial direction outside.

  In the heavy duty tire of the present invention, the bead portion is provided with a bead apex rubber extending from the bead core to the outer side in the tire radial direction between the main body portion and the folded portion, and the bead apex rubber includes an inner apex and An outer apex disposed on the outer side in the tire radial direction of the inner apex and having a rubber hardness smaller than that of the inner apex, and on the inner side in the tire axial direction of the main body portion of the carcass ply, the first steel cord ply The outer end in the tire radial direction of the tire and the outer end in the tire radial direction of the second steel cord ply are both positioned on the inner side in the tire radial direction of the outer end in the tire radial direction of the inner apex. Is desirable.

  In the heavy duty tire according to the present invention, an outer end in the tire radial direction of the first steel cord ply is positioned on an outer side in the tire radial direction with respect to an outer end of the turned-up portion on the inner side in the tire axial direction of the main body. The outer end of the second steel cord ply on the side of the folded portion and the outer end on the side of the main body portion are preferably located on the inner side in the tire radial direction than the outer end of the folded portion.

  In the heavy load tire of the present invention, the outer end in the tire radial direction of the first organic fiber cord ply and the outer end of the second organic fiber cord ply in the tire radial direction are outside the folded portion in the tire axial direction. In any case, it is preferable that the first organic fiber cord ply is located on the outer side in the tire radial direction from the outer end of the folded portion, and the first organic fiber cord ply covers the outer end of the second organic fiber cord ply.

  In the heavy duty tire of the present invention, the inner end of the second reinforcing portion in the tire radial direction is located on the outer side in the tire axial direction from the bead core, and the bead is attached to a normal rim and loaded with a normal internal pressure. The distance in the tire radial direction from the base line to the inner end of the second reinforcing portion is not more than 0.6 times the flange height from the bead base line to the outer end in the tire radial direction of the flange of the regular rim. It is desirable.

  In the heavy duty tire of the present invention, the second reinforcing portion is adjacent to the ply in which a distance between the cord of the first organic fiber cord ply and the cord of the second organic fiber cord ply is 0.5 to 1.8 mm. It is desirable to have a part.

  In the heavy load tire of the present invention, an inner end in the tire radial direction of the first steel cord ply is positioned on an inner side in the tire axial direction of the main body portion, and an inner end in the tire radial direction of the first organic fiber cord ply is The inner end in the tire radial direction of the second organic fiber cord ply is located outside the inner end of the first steel cord ply and the inner end of the first steel cord ply in the tire radial direction. It is desirable to be located on the outer side in the tire axial direction and on the inner side in the tire radial direction than the inner end of the first steel cord ply.

  In the heavy duty tire of the present invention, the bead core has an upper surface extending in the tire axial direction on the outer side in the tire radial direction, and the inner end of the first steel cord ply and the inner end of the second organic fiber cord ply. It is desirable that an end is positioned on the inner side in the tire radial direction from the upper surface of the bead core, and the inner end of the first organic fiber cord ply is positioned on the outer side in the tire radial direction from the upper surface of the bead core. .

  The bead portion of the heavy duty tire of the present invention includes a first reinforcing portion extending at least partially in the tire radial direction inside the main body portion of the carcass ply in the tire radial direction, and at least a portion of the tire shaft of the folded portion of the carcass ply. A second reinforcing portion extending in the tire radial direction on the outer side in the direction is provided.

  The first reinforcing portion includes a first steel cord ply extending in the tire radial direction along an inner side in the tire axial direction of the main body portion, and at least a part of the first reinforcing cord overlaps with the first steel cord ply, and around the bead core in the tire axial direction. The second steel cord ply has a substantially U-shaped cross section that is wound up from the inside to the outside and has an outer end that terminates on the inner side in the tire radial direction from the outer end of the folded portion. In such a first reinforcing portion, the first steel cord ply and the second steel cord ply are integrated to increase the bending rigidity of the bead portion, and as a result, the bead portion having the bead core as a fulcrum has a large outside in the tire axial direction. Bending deformation can be effectively suppressed.

  The second reinforcing portion includes a first organic fiber cord ply and a second organic fiber cord ply that cover the outer end of the second steel cord ply on the folded portion side from the outer side in the tire axial direction. The organic fiber cord ply has higher flexibility than the steel cord ply and has excellent adhesion to the rubber member. For this reason, the 2nd reinforcement part comprised by the 2 sheets of organic fiber cord ply can relieve | moderate the stress in the outer end of a 2nd steel cord ply, and can suppress the separation there over a long term.

It is sectional drawing of the tire for heavy loads of one Embodiment of this invention. It is an expanded sectional view of the bead part of Drawing 1. It is an enlarged view of the ply adjacent part of the 2nd reinforcement part of FIG. It is an expanded sectional view of the bead part of other embodiments of the present invention. It is an expanded sectional view of the bead part of other embodiments of the present invention. It is an expanded sectional view of the bead part of the tire for heavy loads of a comparative example.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a tire meridian cross-sectional view including a rotating shaft in a normal state of a heavy duty tire (hereinafter, simply referred to as “tire”) 1 of the present embodiment. The tire 1 of the present embodiment is a tube tire in which a tube (not shown) is mounted in the tire lumen, but is not limited to such an aspect.

  The “normal state” is a no-load state in which the tire is assembled on the normal rim R and filled with the normal internal pressure. Hereinafter, unless otherwise specified, the dimensions and the like of each part of the tire are values measured in this normal state.

  The “regular rim” is a rim defined for each tire in the standard system including the standard on which the tire is based. For example, “Standard Rim” for JATMA, “Design Rim” for TRA, For ETRTO, "Measuring Rim".

  “Regular internal pressure” is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based. “JAMATA” is the “highest air pressure”, TRA is the table “TIRE LOAD LIMITS AT” The maximum value described in “VARIOUS COLD INFLATION PRESSURES”, “INFLATION PRESSURE” for ETRTO.

  As shown in FIG. 1, the tire 1 of the present embodiment has a toroidal carcass 6 that extends from the tread portion 2 to the side wall portion 3 and reaches the bead core 5 of the bead portion 4. The carcass 6 is formed from, for example, at least one carcass ply 6A. The carcass ply 6A is configured, for example, by arranging steel carcass cords at an angle of 70 to 90 ° with respect to the tire circumferential direction.

  The carcass ply 6A includes a main body portion 6a and a folded portion 6b. The main body portion 6 a reaches the bead core 5 of the bead portion 4 from the tread portion 2 through the sidewall portion 3. The folded portion 6b is connected to the main body portion 6a and is folded around the bead core 5 from the inner side in the tire axial direction to the outer side.

  As a desirable mode, a belt layer 7 is disposed outside the carcass 6 in the radial direction and inside the tread portion 2. The belt layer 7 is formed of, for example, a plurality of belt plies using steel belt cords. The belt layer 7 of the present embodiment has a four-sheet structure formed of, for example, first to fourth belt plies 7A to 7D.

  FIG. 2 shows an enlarged view of the bead portion 4. The bead portion 4 is provided with a bead apex rubber 8 extending from the bead core 5 to the outside in the tire radial direction, and a first reinforcement portion 11 and a second reinforcement portion 12 for reinforcing the bead portion 4.

  The bead core 5 is formed in, for example, a polygonal cross section in which steel bead wires are wound in multiple rows and multiple stages. The bead core 5 of the present embodiment has, for example, a flat hexagonal cross section, and has an upper surface 5a extending in the tire axial direction on the outer side in the tire radial direction and a lower surface 5b extending in the tire axial direction on the inner side in the tire radial direction. . As a desirable mode, bead core 5 of this embodiment contains core body 9 constituted by a bead wire, for example, and wrapping layer 10 covering the circumference of core body 9. The wrapping layer 10 is made of an organic fiber campus cloth such as nylon, for example, and fixes a bead wire.

  For example, the bead apex rubber 8 is tapered from the bead core 5 toward the outer side in the tire radial direction. The bead apex rubber 8 of the present embodiment includes, for example, an inner apex 13 and an outer apex 14 disposed on the outer side in the tire radial direction of the inner apex 13.

  The inner apex 13 is formed in, for example, a substantially triangular cross section extending from the bead core 5 to the outer side in the tire radial direction between the main body portion 6a and the folded portion 6b. The outer end 15 in the tire radial direction of the inner apex 13 is located, for example, on the outer surface in the tire axial direction of the main body 6a. For example, the outer end 15 of the inner apex 13 is preferably located on the outer side in the tire radial direction with respect to the outer end 16 of the folded portion 6b.

  For example, the inner apex 13 is preferably made of hard rubber having a rubber hardness of 80 to 95 °. In the present specification, “rubber hardness” means durometer A hardness measured in a 23 ° C. environment by durometer type A based on JIS-K6253.

  The outer apex 14 is formed with rubber hardness smaller than that of the inner apex 13, for example. For example, the outer apex 14 is connected to the inner apex 13 via a boundary surface 17 that extends radially inward from the outer end 15 of the inner apex 13 toward the folded portion 6b.

  The first reinforcing portion 11 includes a first steel cord ply 21 and a second steel cord ply 22. In each of the steel cord plies 21 and 22, for example, a plurality of steel cords are inclined and arranged at an angle of 20 to 60 ° with respect to the tire circumferential direction. The steel cords of the first steel cord ply 21 and the steel cords of the second steel cord ply 22 are, for example, inclinedly arranged in opposite directions. In each ply 21, 22, the number of steel cords arranged is preferably 20 to 40 per 50 mm ply width, for example.

  The first steel cord ply 21 extends in the tire radial direction along the inner side in the tire axial direction of the main body portion 6a. For example, at least a part of the first steel cord ply 21 of the present embodiment is in contact with the main body 6a. However, the arrangement of the first steel cord ply 21 is not limited to such an aspect.

  The outer end 23 in the tire radial direction of the first steel cord ply 21 is positioned, for example, on the outer side in the tire radial direction with respect to the outer end 16 of the folded portion 6b. Thereby, the bending rigidity inside the tire axial direction of the bead portion 4 is effectively enhanced. For example, the outer end 23 of the first steel cord ply is located on the inner side in the tire radial direction than the outer end 15 of the inner apex 13. As a result, the concentration of strain near the outer end 23 of the first steel cord ply 21 is suppressed. Therefore, the separation starting from the outer end 23 is suppressed.

  In order to suppress separation starting from the outer end 23 while increasing the rigidity of the bead portion 4, the height H2 in the tire radial direction from the bead base line BL to the outer end 23 of the first steel cord ply 21 is: For example, the inner apex height H1 in the tire radial direction from the bead base line BL to the outer end 15 of the inner apex 13 is preferably 0.85 to 0.95 times. In the present specification, the bead base line BL means a tire axial direction line passing through a rim diameter position determined by a standard based on the tire.

  The inner end 24 in the tire radial direction of the first steel cord ply 21 is located, for example, on the inner side in the tire axial direction of the main body 6a. As a desirable mode, for example, the inner end 24 of the first steel cord ply 21 is located on the inner side in the tire radial direction with respect to the upper surface 5a of the bead core 5 and on the outer side in the tire radial direction with respect to the lower surface 5b of the bead core 5. When a load is applied to the tire, the vicinity of the bead core 5 hardly deforms. Therefore, according to the present embodiment, separation starting from the inner end 24 of the first steel cord ply 21 is suppressed.

  The second steel cord ply 22 has a substantially U-shaped cross section wound around the bead core 5 from the inner side in the tire axial direction to the outer side. On the main body 6 a side, the outer end 25 in the tire radial direction of the second steel cord ply 22 is located on the outer side in the tire radial direction of the inner end 24 of the first steel cord ply 21. Thereby, at least a part of the second steel cord ply 22 overlaps the first steel cord ply 21.

  As a desirable mode, outer end 25 of the 2nd steel cord ply 22 is located in the tire radial direction inner side rather than outer end 15 of inner apex 13 and outer end 23 of the 1st steel cord ply 21, for example. As a more desirable mode, the outer end 25 of the second steel cord ply 22 is located on the inner side in the tire radial direction than the outer end 16 of the folded portion 6b. Thereby, in the present embodiment, the outer end 16 of the folded portion 6b is located between the outer end 23 of the first steel cord ply 21 and the outer end 25 of the second steel cord ply 22 in the tire radial direction. Thereby, the outer end position of the ply is dispersed in the tire radial direction, the rigidity distribution of the bead portion 4 becomes smooth, and the stress concentration in the bead portion 4 is suppressed.

  In order to further exert the above-described effects, the height H3 in the tire radial direction from the bead base line BL to the outer end 25 on the main body 6a side of the second steel cord ply 22 is preferably the inner apex height H1. 0.55 times or more, more preferably 0.60 times or more, preferably 0.70 times or less, more preferably 0.65 times or less.

  On the folded portion 6b side, the outer end 26 of the second steel cord ply 22 is located on the inner side in the tire radial direction than the outer end 16 of the folded portion 6b. Such a second steel cord ply 22 is useful for enhancing the ride comfort without excessively increasing the rigidity of the bead portion 4 on the outer side in the tire axial direction.

  In the first reinforcing portion 11 constituted by the first steel cord ply 21 and the second steel cord ply 22 as described above, the plies 21 and 22 are integrated to increase the bending rigidity of the bead portion 4, and thus the bead core. A large bending deformation of the bead portion 4 with the fulcrum 5 at the outer side in the tire axial direction can be effectively suppressed.

  The second reinforcing portion 12 includes a first organic fiber cord ply 31 and a second organic fiber cord ply 32. In each of the organic fiber cord plies 31, 32, for example, a plurality of organic fiber cords are inclined and arranged at an angle of 20 to 60 ° with respect to the tire circumferential direction. Each cord of the first organic fiber cord ply 31 and each cord of the second organic fiber cord ply 32 are, for example, inclinedly arranged in opposite directions.

  In each ply 31, 32, the number of organic fiber cords arranged is preferably 20 to 40 per ply width of 50 mm, for example. As the organic fiber cord, for example, a nylon cord, a polyester cord, an aromatic polyamide cord, a high-tensile vinylon cord, or the like is preferably used. Such an organic fiber cord ply is more flexible than a steel cord ply and has excellent adhesion to a rubber member.

  The first organic fiber cord ply 31 and the second organic fiber cord ply 32 overlap each other and cover the outer end 26 on the folded portion 6b side of the second steel cord ply 22 from the outer side in the tire axial direction. Since the second reinforcing portion 12 composed of two organic fiber cord plies has flexibility and adhesion to a rubber member superior to those of the steel cord plies, the outer ends of the second steel cord plies 22 The stress at 24 can be relaxed and the separation there can be suppressed over a long period of time.

  The outer end 33 in the tire radial direction of the first organic fiber cord ply 31 is located on the outer side in the tire radial direction with respect to the outer end 16 of the folded portion 6b. As a desirable mode, the outer end 33 of the first organic fiber cord ply 31 is located outside the outer end 15 of the inner apex 13 in the tire radial direction. Specifically, the height H4 in the tire radial direction from the bead base line BL to the outer end 33 of the first organic fiber cord ply 31 is, for example, 1.05 to 1.15 times the inner apex height H1. is there.

  As a further desirable mode, the outer end 33 of the first organic fiber cord ply 31 is located on the inner side in the tire radial direction than the outer end 18 of the outer apex 14. As a result, the concentration of strain near the outer end 33 of the first organic fiber cord ply 31 is suppressed, and separation starting from the outer end 33 is suppressed.

  The inner end 34 in the tire radial direction of the first organic fiber cord ply 31 is located on the outer side in the tire axial direction of the folded portion 6 b and on the outer side in the tire radial direction with respect to the inner end 24 of the first steel cord ply 21. As a desirable mode, the inner end 34 of the first organic fiber cord ply 31 is located outside the upper surface 5a of the bead core 5 in the tire radial direction. When the tire is running, deformation near the inner end 34 of the first organic fiber cord ply 31 is suppressed by the rim flange, and the distortion is relatively small. For this reason, even if the 1st organic fiber cord ply 31 is shortened as mentioned above, there is no possibility of separation and a tire can be reduced in weight.

  The outer end 35 in the tire radial direction of the second organic fiber cord ply 32 is located on the outer side in the tire radial direction with respect to the outer end 16 of the folded portion 6b. Thereby, the 2nd organic fiber cord ply 32 has covered the outer end 16 of the folding | turning part 6b. Therefore, the separation starting from the outer end 16 of the folded portion 6b is effectively suppressed.

  As a desirable mode, for example, the outer end 35 of the second organic fiber cord ply 32 is located on the inner side in the tire radial direction from the outer end 33 of the first organic fiber cord ply 31 in the tire radial direction, and the first organic fiber cord ply 31 is covered. Thereby, the separation starting from the outer end 35 of the second organic fiber cord ply 32 is effectively suppressed.

  As a more desirable mode, the height H5 in the tire radial direction from the bead base line BL to the outer end 35 of the second organic fiber cord ply 32 is 0.95 to 1.05 times the inner apex height H1. Such a second organic fiber cord ply 32 can effectively suppress bending deformation of the bead portion 4 outward in the tire axial direction in cooperation with the inner apex 13.

  The inner end 36 in the tire radial direction of the second organic fiber cord ply 32 is located on the outer side in the tire axial direction of the folded portion 6 b and on the inner side in the tire radial direction of the inner end 34 of the first organic fiber cord ply 31.

  As a desirable aspect, the inner end 36 of the second organic fiber cord ply 32 is disposed, for example, on the inner side in the tire radial direction from the upper surface 5 a of the bead core 5 and on the outer side in the tire radial direction from the lower surface 5 b of the bead core 5. Even when a load is applied to the tire, the vicinity of the bead core 5 is hardly deformed, so that the separation starting from the inner end 36 of the second organic fiber cord ply 32 is suppressed.

  As a more desirable mode, it is desirable that the inner end 36 of the second organic fiber cord ply 32 is located, for example, on the inner side in the tire radial direction than the inner end 24 of the first steel cord ply 21. Thereby, the position of the inner end of each ply that is likely to be a rigid step is dispersed, and as a result, damage to the bead portion such as separation is suppressed.

  In the normal state, the distance L1 in the tire radial direction from the bead base line BL to the inner end 37 in the tire radial direction of the second reinforcing portion 12 (in the present embodiment, the inner end 36 of the second organic fiber cord ply 32) is The flange height Hf from the bead base line BL to the outer end of the regular rim flange in the tire radial direction is preferably 0.6 times or less. As a result, the shear stress acting on the inner end 37 of the second reinforcing portion 12 is reduced, and as a result, separation starting from the inner end 37 is suppressed.

  In order to further exert the above effect, in the present embodiment, the distance L2 in the tire radial direction from the bead base line BL to the inner end 34 of the first organic fiber cord ply 31 is 0.6 of the flange height Hf. It is not more than twice, more preferably not more than 0.5 times.

  The second reinforcing portion 12 has a ply adjacent portion 38 where the organic fiber cord plies 31 and 32 are adjacent to each other. As shown in FIG. 3, in the ply adjacent portion 38, the interval t1 between the cord 31c of the first organic fiber cord ply 31 and the cord 32c of the second organic fiber cord ply 32 is, for example, 0.5 to 1.. 8 mm is desirable. Such a ply adjacent portion 38 can effectively absorb the shear strain generated between the organic fiber cord plies 31 and 32.

  4 and 5 are enlarged views of a bead portion of a heavy duty tire according to another embodiment of the present invention. 4 and 5, the same reference numerals are given to the configurations common to the above-described embodiments.

  In the embodiment shown in FIG. 4, the inner end 37 of the second reinforcing portion 12 is disposed on the inner side in the tire radial direction of the bead core 5. In such an embodiment, the inner end 37 of the second reinforcing portion 12 is fixed between the bead core 5 and the rim flange, and separation starting from the inner end 37 is effectively suppressed.

  In the embodiment shown in FIG. 5, the inner end 37 of the second reinforcing portion 12 is located inside the bead core 5 in the tire axial direction. Such a 2nd reinforcement part 12 can further reinforce the bead part 4, and is useful for suppressing the bending deformation.

  In the embodiment shown in FIGS. 4 and 5, the inner end 37 of the second organic fiber cord ply 32 constitutes the inner end 37 of the second reinforcing portion. However, it is not limited to such an aspect, The inner end 34 of the 1st organic fiber cord ply 31 may comprise the inner end 37 of a 2nd reinforcement part. In such an embodiment, since the first organic fiber cord ply 31 covers the inner end 36 of the second organic fiber cord ply 32, the durability of the bead portion 4 is further enhanced.

  As mentioned above, although the heavy duty tire of one embodiment of the present invention was explained in detail, the present invention is not limited to the above-mentioned specific embodiment, and can be carried out by being changed to various aspects.

A heavy-duty tire of size 12.00R20 having the basic structure of FIG. 1 and the bead portion of FIG. 2, FIG. 4, or FIG. As a comparative example, as shown in FIG. 6, a heavy-duty tire having a bead portion provided with only the first reinforcing portion was prototyped. The durability of the bead portion of each test tire was tested. The common specifications and test methods for each test tire are as follows.
Wearing rim: 20 × 8.50V
Tire internal pressure: 850kPa

<Durability of bead part>
The test tire was run on the drum tester under the following conditions, and the running distance until the bead portion was damaged was measured. A result is an index which sets a comparative example as 100, and shows that durability of a bead part is excellent, so that a numerical value is large.
Speed: 20km / h
Longitudinal load: 73.46KN
The test results are shown in Table 1.

  As a result of the test, it was confirmed that the durability of the bead portion of the tire of the example was improved.

2 tread portion 3 sidewall portion 4 bead portion 5 bead core 6a main body portion 6b folded portion 6A carcass ply 6 carcass 11 first reinforcing portion 12 second reinforcing portion 21 first steel cord ply 22 second steel cord ply 31 first organic fiber Cord ply 32 Second organic fiber cord ply

Claims (8)

A carcass comprising a carcass ply including a main body part extending from a tread part through a sidewall part to a bead core of the bead part and a turn-back part connected to the main body part and turning back around the bead core from the inner side to the outer side in the tire axial direction. A heavy duty tire,
The bead portion includes at least a first reinforcing portion extending in the tire radial direction inside the main body portion in the tire axial direction, and at least a second portion extending in the tire radial direction outside the folded portion in the tire axial direction. A reinforcing part is provided,
The first reinforcing portion includes a first steel cord ply extending in a tire radial direction along an inner side in the tire axial direction of the main body portion, and at least a part of the first reinforcing portion overlaps with the first steel cord ply, and a tire around the bead core. A second steel cord ply having a substantially U-shaped cross section that is wound from the inner side in the axial direction to the outer side and that has an outer end that terminates in the tire radial direction inner side than the outer end of the folded portion,
The second reinforcing portion is a heavy duty tire including a first organic fiber cord ply and a second organic fiber cord ply that cover the outer end of the second steel cord ply on the folded portion side from the outer side in the tire axial direction. The bead portion is provided with a bead apex rubber extending from the bead core to the outside in the tire radial direction between the main body portion and the folded portion.
The bead apex rubber includes an inner apex and an outer apex that is disposed on the outer side in the tire radial direction of the inner apex and has a rubber hardness smaller than that of the inner apex,
On the inner side in the tire axial direction of the main body portion of the carcass ply, the outer end in the tire radial direction of the first steel cord ply and the outer end in the tire radial direction of the second steel cord ply are both The heavy duty tire according to claim 1, wherein the heavy duty tire is located on the inner side in the tire radial direction from the outer end in the tire radial direction of the apex. On the inner side in the tire axial direction of the main body portion, the outer end in the tire radial direction of the first steel cord ply is located on the outer side in the tire radial direction with respect to the outer end of the folded portion,
The outer end on the folded portion side and the outer end on the main body portion side of the second steel cord ply are both positioned on the inner side in the tire radial direction with respect to the outer end of the folded portion. Heavy duty tire. The outer end in the tire radial direction of the first organic fiber cord ply and the outer end in the tire radial direction of the second organic fiber cord ply are both outside of the folded portion on the outer side in the tire axial direction of the folded portion. Located on the outer side in the tire radial direction than the end,
The heavy duty tire according to any one of claims 1 to 3, wherein the first organic fiber cord ply covers the outer end of the second organic fiber cord ply. The inner end of the second reinforcing portion in the tire radial direction is located on the outer side in the tire axial direction than the bead core,
In a normal state in which a normal internal pressure is applied to the normal rim, the distance in the tire radial direction from the bead base line to the inner end of the second reinforcing portion is the tire radius of the flange of the normal rim from the bead base line. The heavy duty tire according to any one of claims 1 to 4, wherein the tire is not more than 0.6 times the height of the flange to the outer end in the direction.   The said 2nd reinforcement part has a ply adjacent part whose space | interval of the cord of the said 1st organic fiber cord ply and the cord of the said 2nd organic fiber cord ply is 0.5-1.8 mm. The heavy duty tire according to any one of the above. The inner end of the first steel cord ply in the tire radial direction is located on the inner side in the tire axial direction of the main body,
The inner end in the tire radial direction of the first organic fiber cord ply is located on the outer side in the tire axial direction of the folded portion and on the outer side in the tire radial direction with respect to the inner end of the first steel cord ply,
The inner end in the tire radial direction of the second organic fiber cord ply is positioned on the outer side in the tire axial direction of the folded portion and on the inner side in the tire radial direction with respect to the inner end of the first steel cord ply. The heavy duty tire according to any one of 6. The bead core has an upper surface extending in the tire axial direction on the outer side in the tire radial direction,
The inner end of the first steel cord ply and the inner end of the second organic fiber cord ply are located on the inner side in the tire radial direction than the upper surface of the bead core,
The heavy duty tire according to claim 7, wherein the inner end of the first organic fiber cord ply is positioned on the outer side in the tire radial direction with respect to the upper surface of the bead core.

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