JP4567763B2 - Heavy duty tire - Google Patents

Description

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

  As shown in FIG. 4, in heavy-duty tires used under high loads, the bead deformation is large. Therefore, a cord loose or the like is formed on the outer end b1e of the folded portion b1 of the carcass ply b that is folded around the bead core a. Damage is likely to occur. Therefore, conventionally, the bead portion c is made from a steel cord ply having a U-shape in which an inner piece portion d2 along the main body portion b2 of the carcass ply b and an outer piece portion d1 along the folded portion b1 are joined by a bottom piece portion. The bead reinforcement layer d is used to enhance the bead rigidity (see, for example, Patent Document 1).

  This bead reinforcing layer d can reduce bead deformation, and in particular, by raising the inner piece portion d2 higher than the folded portion b1, the distortion generated at the outer end b1e is reduced, and at the outer end b1e. Damage can be suppressed.

JP-A-55-106807

  However, in such a conventional structure, stress concentration is caused at the outer end d2e of the inner piece part d2 raised to a high level. Therefore, new damage starting from the outer end d2e is induced. It was not possible to improve it. When the outer piece d1 is raised higher than the folded portion b1 instead of the inner piece d2, the outer piece d1 is distorted on the compression side. In comparison, the occurrence of damage becomes more prominent.

  Therefore, the present invention is basically based on forming the bead apex rubber with a high elastic inner apex and a low elastic outer apex, and raising the inner apex beyond the inner piece of the bead reinforcing layer radially outward. An object of the present invention is to provide a heavy-duty tire that can suppress damage at the outer end of the folded portion of the carcass ply and the outer end of the inner piece portion of the bead reinforcement layer and can achieve further improvement in bead durability. It is said.

In order to achieve the above object, the invention of claim 1 of the present application is directed to both ends of the ply main body part extending from the tread part through the sidewall part to the bead core of the bead part, and around the bead core from the inner side to the outer side in the tire axial direction. A carcass made of a carcass ply with a series of folded ply folding parts;
A bead apex rubber extending between the bead core and the tire radial direction through between the ply folded portion and the ply body portion;
An inner piece portion extending in the radial direction along the tire axial direction inner side surface of the ply body portion and an outer piece portion extending in the radial direction along the tire axial direction outer side surface of the ply folded portion are radially inward of the bead core. U-shaped bead reinforcement layer connected in series by a bottom piece passing through
And a heavy duty tire comprising clinch rubber for preventing rim displacement, which is disposed on the outer side in the tire axial direction of the outer piece portion and has a rising portion that forms the outer surface of the bead portion,
The bead apex rubber has a triangular cross-section rising from the bead core and a radially inner inner apex portion made of highly elastic rubber having a vertex on the tire axially outer surface of the ply main body portion, and the ply from the apex. It consists of the outer apex part which is connected to the inner apex part via a boundary surface extending inward in the radial direction toward the turned-up part and is made of rubber having a lower elasticity than the inner apex part.
The radial height HPi from the bead base line of the radially outer end of the inner piece portion of the bead reinforcement layer is larger than the radial height HN from the bead base line of the radially outer end of the ply turn-up portion,
And the radial height HEi from the bead base line of the apex of the inner apex portion is larger than the radial height HPi of the inner piece portion,
In addition, the tire axial direction line passing through the radially outer end of the outer piece portion of the bead reinforcing layer extends from the intersection where the ply folding portion intersects the inner side surface in the tire axial direction on the second reference line orthogonal to the ply main body portion. While setting the rubber thickness T2i of the inner apex portion to 10 to 25% of the maximum width Wc in the tire axial direction of the bead core,
The rubber thickness T2o of the outer apex portion on the second reference line extends from the radially outer end of the ply turn-up portion to the total rubber of the bead apex rubber on the first reference line orthogonal to the ply main body portion. 70-100% of the thickness T1 ,
Each outer end of the bead reinforcement layer and the outer end of the inner piece are covered and protected by edge cover rubber,
Between the ply folded portion and the clinch rubber, an inner and outer protective rubber is interposed,
The inner protective rubber rises from an edge cover rubber that covers the outer piece portion, and terminates beyond the outer end of the ply folded portion outward in the radial direction.
The outer protective rubber is interposed between the outer piece portion and the clinch rubber at a radially inner end from the inner protective rubber, and is an outer apex portion at a radial outer end from the inner protective rubber. Between the rubber and clinch rubber,
The edge cover rubber and the inner and outer protective rubbers use natural rubber as a rubber component in an amount of 50% by mass or more, have a complex elastic modulus E * 4 in the range of 5 to 13 MPa, and have a complex elastic modulus E * 3 of clinch rubber. It is characterized by being smaller .

  In the invention of claim 2, the rubber thickness J3c of the clinch rubber on the third reference line extending from the radially outer end of the ply turn-up portion and perpendicular to the outer surface of the bead portion is set on the third reference line. It is characterized by being 20 to 40% of the total rubber thickness J3 from the radially outer end of the ply turn-up portion to the outer surface of the bead portion.

In the invention of claim 3, when the tire cross-sectional height is H, the radial height HN of the ply folded portion, the radial height HPi of the inner piece portion of the bead reinforcing layer, and the inner apex portion The radial height HEi is characterized by satisfying the following conditions.
0.15H ≦ HN ≦ 0.35H
0.16H ≦ HPi ≦ 0.36H
0.17H ≦ HEi ≦ 0.37H

In the invention of claim 4, the rubber thickness T2i of the inner apex portion on the second reference line, the rubber thickness T2o of the outer apex portion, and the total rubber thickness T1 of the bead apex rubber on the first reference line. Is characterized by satisfying the following conditions.
0.6Wc ≦ (T2i + T2o) ≦ 1.0Wc
0.6Wc ≦ T1 ≦ 1.0Wc
0.5Wc ≦ T2o ≦ 0.7Wc

In the invention of claim 5, the rubber thickness J3c and the total rubber thickness J3 of the clinch rubber on the third reference line satisfy the following conditions.
0.6Wc ≦ J3 ≦ 1.2Wc
0.15Wc ≦ J3c ≦ 0.6Wc

  Further, in the invention of claim 6, the radial height HC from the bead base line of the radially outer end of the clinch rubber is 0.2 to 0.4 times the sectional height H of the tire. Yes.

  Further, in this specification, unless otherwise specified, the dimensions and the like of each part of the tire are values specified when the bead part is held in accordance with the rim width specified by the tire size in a non-rim assembled state. .

  In the present invention, as described above, the radial height HPi of the inner piece portion of the bead reinforcing layer is set to be larger than the radial height HN of the ply turn-up portion. Therefore, bead deformation can be reduced, and distortion generated at the outer end of the ply turn-up portion can be reduced. In addition, the rubber thickness T2o of the outer apex portion (low elastic rubber) on the second reference line is secured to 70 to 100% of the total rubber thickness T1 of the bead apex rubber on the first reference line. Therefore, when the bead is deformed, the shear strain between the bead apex rubber acting on the outer end of the ply folded portion can be reduced by the expansion and contraction of the low elastic rubber in the outer apex portion, and the effect of the inner piece portion of the bead reinforcement layer In combination with this, it is possible to effectively suppress damage at the outer end of the ply turn-up portion.

  On the other hand, the radial height HEi of the inner apex portion (high elastic rubber) is set to be larger than the radial height HPi of the inner piece portion. Therefore, deformation at the outer end of the inner piece portion can be suppressed by the highly elastic inner apex portion, and damage at the outer end of the inner piece portion can be effectively suppressed. Moreover, the rubber thickness T2i of the inner apex portion on the second reference line is set as low as 10 to 25% of the maximum width Wc in the tire axial direction of the bead core. Therefore, the shear strain between the inner apex portion and the ply main body portion can be kept low, and separation between the ply main body portion newly generated due to the inner apex portion can be suppressed.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of a heavy duty tire according to the present invention, and FIG. 2 is an enlarged cross-sectional view of a bead portion thereof.

  As shown in FIG. 1, the heavy load tire 1 according to the present embodiment includes a toroidal carcass 6 extending from a tread portion 2 through a sidewall portion 3 to a bead core 5 of a bead portion 4, and from the bead core 5 in the tire radial direction outer side. It includes a bead apex rubber 8 that extends, a U-shaped bead reinforcing layer 9 that reinforces the bead portion 4, and a clinch rubber 10 that prevents the rim from slipping out of the bead portion 4.

  The carcass 6 is formed of a single carcass ply 6A in which steel carcass cords are arranged at an angle of 70 to 90 ° with respect to the tire circumferential direction. The carcass ply 6A includes a series of ply folding portions 6b that are folded around the bead core 5 from the inner side to the outer side in the tire axial direction at both ends of the ply main body portion 6a straddling the bead cores 5 and 5.

  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 at least two belt plies using a steel belt cord. In this example, the first belt ply 7A in which the belt cord is arranged at an angle of, for example, 60 ± 15 ° with respect to the tire circumferential direction, and the belt cord is placed on the outer side and the belt cord is, for example, 10 The thing of the 4 sheet structure which consists of the 2nd-4th belt plies 7B-7D arranged at a small angle of -35 degrees is illustrated.

  As shown in an enlarged view in FIG. 2, the bead portion 4 is provided with a bead apex rubber 8 that extends between the ply turn-up portion 6b and the ply body portion 6a and extends outward from the bead core 5 in the tire radial direction. Is done. The bead core 5 has a core body 5A having a polygonal cross section (for example, a hexagonal cross section) in which, for example, steel bead wires are wound in multiple rows and stages. In this example, the core body 5A is surrounded by a bead wire. The case where it coat | covers with well-known wrapping layers 5B, such as a rubber layer and a canvas layer, etc. which prevent a variation is illustrated. Further, in this example, the heavy load tire 1 applied to the flat bottom rim is illustrated, but the heavy load tire 1 applied to a 15 ° deep bottom rim may be used.

  The bead apex rubber 8 is made of a highly elastic rubber and is arranged on the inner side in the radial direction 8A, and the outer apex is made of a rubber having a lower elasticity than the inner apex portion 8A and is arranged on the outer side in the radial direction. Part 8B. The inner apex portion 8A rises from the bead core 5 and has a triangular cross section having a vertex P1 on the outer surface in the tire axial direction of the ply main body portion 6a. The outer apex portion 8B is connected to the inner apex portion 8A via a boundary surface 8S extending inward in the radial direction from the apex P1 toward the ply turn-up portion 6b.

  A radially outer end 8E of the outer apex portion 8B that forms a radially outer end 8E of the bead apex rubber 8 is located radially outward from a radially outer end 6E of the ply turn-up portion 6b, and the boundary surface The other end P2 of 8S is located on the inner side surface in the tire axial direction of the ply turn-up portion 6b and radially inward from the upper end (not shown) of the rim flange. Accordingly, in the region radially outward from the upper end of the rim flange where the bead portion 4 is greatly deformed, the ply turn-up portion 6b is adjacent to the low-elasticity outer apex portion 8B, and the outer end 6E is the outer apex portion 8B. Terminate while touching. As a result, the shear strain generated between the ply folding portion 6b and the bead apex rubber 8 when the bead is deformed can be absorbed and relaxed by the expansion and contraction of the low elastic rubber in the outer apex portion 8B.

  Here, a high elastic rubber having a complex elastic modulus E * 1 of 20 to 70 MPa is suitable for the inner apex portion 8A, and a complex elastic modulus E * 2 of 2.0 to 6 is preferable for the outer apex portion 8B. A low-elasticity rubber of 0.0 MPa is suitable. If the complex elastic modulus E * 1 is less than 20 MPa, it is difficult to ensure the required bead rigidity, which leads to a decrease in steering stability and a decrease in bead durability. On the other hand, when the complex elastic modulus E * 1 exceeds 70 MPa, the bead rigidity becomes excessive and the riding comfort is lowered. From such a viewpoint, the lower limit of the complex elastic modulus E * 1 is preferably 35 MPa or more, and the upper limit is preferably 60 MPa or less. In the outer apex portion 8B, if the complex elastic modulus E * 2 is less than 2.0 MPa, the bead deformation is insufficient due to insufficient bead rigidity, and if it exceeds 6.0 MPa, the above-described shear strain relaxation effect is obtained. In any case, such as damage, it is disadvantageous to bead durability. The complex elastic modulus is a value measured using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho Co., Ltd. under conditions of a temperature of 70 ° C., a frequency of 10 Hz, an initial strain of 10%, and an amplitude of ± 1%.

  Next, the bead reinforcing layer 9 includes an inner piece portion 9i extending in the radial direction along the tire axial direction inner side surface of the ply body portion 6a, and a tire axial direction outer surface of the ply folded portion 6b in the radial direction. The extending outer piece 9o is formed in a U-shape that is connected by a bottom piece 9A that passes through the inside of the bead core 5 in the radial direction. The bead reinforcing layer 9 is composed of one reinforcing ply in which steel reinforcing cords are inclined and arranged at an angle of, for example, 40 to 70 ° with respect to the tire circumferential direction, and the bending rigidity is increased by intersecting with the carcass cord. The bead portion 4 is strongly reinforced. If the angle of the reinforcing cord is less than 40 ° or exceeds 70 °, the crossing angle with the carcass cord is too small or too large, the reinforcing effect is insufficient, and the bead rigidity cannot be sufficiently increased.

  Next, the clinch rubber 10 has a rising portion 10A that is disposed on the outer side in the tire axial direction of the outer piece portion 9o and extends radially outward from the bead heel portion Bh. The raised portion 10A is exposed at least in the flange contact range where it comes into contact with the rim flange, and forms the outer surface 4S1 of the bead portion 4. In this example, the case where the clinch rubber 10 includes a base portion 10B extending inward in the tire axial direction from the bead heel portion Bh to the bead toe portion Bt and forming the bottom surface 4S2 of the bead portion 4 is exemplified.

  The clinch rubber 10 needs to have sufficient wear resistance and hardness, and is preferably made of rubber having a complex elastic modulus E * 3 in the range of 8 to 15 MPa and lower elasticity than the inner apex portion 8A. A sidewall rubber 3G having a lower elasticity than the clinch rubber 10 and the outer apex portion 8B is continuously provided on the radially outer side of the rising portion 10A. The boundary line 10S between the rising portion 10A and the sidewall rubber 3G extends from the lower point Q1 on the outer side surface 4S1 of the bead portion 4 to the outer apex portion 8B in a radially outward direction.

  In the present invention, the radial height HPi from the bead base line BL of the radially outer end 9iE of the inner piece 9i of the bead reinforcement layer 9 is set to the bead baseline of the radially outer end 6E of the ply turn-up portion 6b. The radial height HEi from the bead base line BL of the apex P1 of the inner apex portion 8A is set to be larger than the radial height HN from BL (HPi> HN), and the radius of the inner piece portion 9i. The direction height HPi is set to be larger (HEi> HPi).

  Thus, by setting HPi> HN and raising the inner piece portion 9i higher than the ply turn-up portion 6b, the outer end 6E of the ply turn-up portion 6b can be protected and distortion generated at the outer end 6E can be reduced. . Further, by setting HEi> HPi and raising the highly elastic inner apex portion 8A higher than the inner piece portion 9i, the outer end 9iE of the inner piece portion 9i can be protected, and the distortion generated at the outer end 9iE can be reduced. The inner apex portion 8A has a triangular cross section, and its thickness gradually decreases toward the apex P1. Therefore, since the rigidity changes smoothly in the vicinity of the vertex P1, stress concentration at the vertex P1 can be reduced.

When the tire cross-sectional height is H (shown in FIG. 1), the heights HN, HPi, and HEi are preferably in the following ranges.
0.15H ≦ HN ≦ 0.35H
0.16H ≦ HPi ≦ 0.36H
0.17H ≦ HEi ≦ 0.37H

When the heights HN, HPi, and HEi deviate from the above ranges, the reinforcement effect by the bead reinforcement layer 9 is insufficient, and the steering stability is lowered, and the bead deformation is increased, resulting in durability. The improvement effect is not sufficiently achieved. On the contrary, when it deviates to the upper limit side, each outer end 6E, 9iE, P1 approaches the tire maximum width position where the tire deformation amount is the largest, and therefore, the durability tends to be lowered. From such a viewpoint, the following range is more preferable.
0.22H ≦ HN ≦ 0.28H
0.24H ≦ HPi ≦ 0.30H
0.27H ≦ HEi ≦ 0.33H

  The height difference (HPi−HN) is preferably 0.05 times or more the height HN of the ply turn-up portion 6b, and the height difference (HEi−HPi) is 0% of the height HN. .05 times or more is preferable.

  Further, the radial height HPo from the bead base line BL of the radially outer end 9oE of the outer piece portion 9o of the bead reinforcing layer 9 is smaller than the height HN of the ply turn-up portion 6b, as in the prior art. And it is larger than the upper end height Hf (not shown) of the rim flange. In the case of HPo> HN, compression-side distortion occurs at the outer end 9oE, so that bead damage occurs more significantly. Further, when HPo <Hf, the bead reinforcement effect is not effectively exhibited.

  Next, as shown in FIG. 3, the intersection point where the tire axial direction line passing through the radially outer end 9oE of the outer piece portion 9o of the bead reinforcement layer 9 intersects the tire axial direction inner side surface of the ply turnup portion 6b is denoted by K. When this occurs, the rubber thickness T2i of the inner apex portion 8A on the second reference line X2 extending from the intersection K and perpendicular to the ply main body portion 6a is 10 to 10 of the maximum width Wc in the tire axial direction of the bead core 5. The range is 25%. The rubber thickness T2o of the outer apex portion 8B on the second reference line X2 extends from the radially outer end 6E of the ply turn-up portion 6b and is perpendicular to the ply main body portion 6a. It is the range of 70 to 100% of the total rubber thickness T1 of the bead apex rubber 8 above.

  Thus, the rubber thickness T2o is secured to 70 to 100% of the rubber thickness T1. Therefore, the shear strain generated between the outer end 6E of the ply folding portion 6b and the bead apex rubber 8 at the time of bead deformation can be alleviated by expansion and contraction of the low elastic rubber in the outer apex portion 8B. Accordingly, in combination with the above-described effect by the inner piece portion 9i of the bead reinforcing layer 9, damage at the outer end 6E can be effectively suppressed. If the rubber thickness T2o is less than 70% of the rubber thickness T1, damage to the outer end 6E cannot be suppressed, for example, the effect of reducing the shear strain at the outer end 6E is impaired. The total thickness (T2i + T2o) of the bead apex rubber 8 on the second reference line X2 is excessive with respect to the thickness T1, and the contour line (so-called ply case line) of the carcass ply main body 6a is uneven. , Which tends to impair durability.

  On the other hand, since the rubber thickness T2i is set as low as 10 to 25% of the maximum tire axial width Wc of the bead core, the shear strain between the inner apex portion 8A and the ply main body portion 6a is reduced. Can be kept low. Therefore, separation between the inner apex portion 8A and the ply main body portion 6a newly generated due to the inner apex portion 8A being raised higher than the inner piece portion 9i can be suppressed, and improvement in durability can be ensured. Is done. If the rubber thickness T2i is less than 10% of the width Wc, damage at the outer end 9iE cannot be suppressed, for example, distortion at the outer end 9iE of the inner piece 9i cannot be sufficiently reduced. On the other hand, if it exceeds 25%, the shear strain between the inner apex portion 8A and the ply main body portion 6a is increased, and separation tends to occur.

At this time, the rubber thicknesses T2i, T2o, and T1 are preferably within the following ranges.
0.6Wc ≦ (T2i + T2o) ≦ 1.0Wc
0.6Wc ≦ T1 ≦ 1.0Wc
0.5Wc ≦ T2o ≦ 0.7Wc
When the range is out of the lower limit side and the upper limit side, the effect of the present invention cannot be exhibited more effectively, and damage is likely to occur at any one of the outer ends 9iE, 6E, and the apex P1. From such a viewpoint, the following ranges are more preferable.
0.7Wc ≦ (T2i + T2o) ≦ 1.0Wc
0.7Wc ≦ T1 ≦ 1.0Wc

  Next, the rubber thickness J3c of the clinch rubber 10 on the third reference line X3 extending from the radially outer end 6E of the ply turn-up portion 6b and perpendicular to the outer surface 4S1 of the bead portion 4 is the third reference The total rubber thickness J3 from the outer end 6E on the line X3 to the outer side surface 4S1 of the bead portion 4 is preferably 20 to 40%. If the rubber thickness J3c is less than 20% of the rubber thickness J3, the movement of the outer end 6E cannot be sufficiently suppressed, and stress tends to concentrate. If the rubber thickness J3c exceeds 40%, the clinch rubber 10 The shear strain increases. Therefore, in any case, the outer end 6E tends to be damaged.

  The rubber thickness J3 is preferably 0.6 to 1.2 times, more preferably 0.6 to 0.8 times the width Wc of the bead core 5, and the rubber thickness J3c is less than 0.6 times. Cannot be sufficiently secured, and stress tends to concentrate on the outer end 6E. Conversely, if it exceeds 1.2 times, an unnecessary weight increase is caused. The rubber thickness J3c is preferably in the range of 0.15 to 0.6 times, more preferably 0.15 to 0.25 times the width Wc of the bead core 5, and when the thickness is less than 0.15 times, the outer end 6E. It is difficult to sufficiently suppress the movement of the stress, and stress tends to concentrate. Conversely, when it exceeds 0.6 times, the shear strain with the clinch rubber 10 increases.

  Further, as shown in FIG. 2, the radial height HC from the bead base line BL of the radially outer end 10E of the clinch rubber 10 is 0.2 to 0.4 times the tire cross-sectional height H, and further 0.3. -0.36 times are preferable. If it is less than 0.2 times, the bead rigidity is reduced and the amount of bead deformation is increased. On the other hand, if it exceeds 0.4 times, the outer end portion of the clinch rubber 10 approaches the maximum tire width position where the amount of tire deformation is the largest, and therefore, between the clinch rubber 10 and the side wall rubber 3G or between the clinch rubber 10 and the bead apex rubber. The shear strain becomes large between 8 and 8, which is disadvantageous for bead durability.

  The height HC of the clinch rubber 10 is larger than the height HN of the ply turn-up portion 6b and smaller than the radial height HE from the bead base line BL of the radially outer end 8E of the bead apex rubber 8. .

In this example, in order to further improve the bead durability, the outer ends 9iE and 9oE of the bead reinforcing layer 9 are covered and protected by a thin edge cover rubber 15 to suppress cord looseness from the outer ends 9iE and 9oE. ing. Further, thin protective rubbers 16i and 16o on the inside and the outside are interposed between the ply folded portion 6b and the clinch rubber 10 to suppress separation between the ply folded portion 6b and the clinch rubber 10, and from the outer end 6E. The cord looseness is suppressed. The inner protective rubber 16i rises from the edge cover rubber 15 and ends beyond the outer end 6E of the ply turn-up portion 6b radially outward. The outer protective rubber 16o is interposed between the outer piece 9o and the clinch rubber 10 at the radially inner end of the inner protective rubber 16i to suppress the separation between the two, and the inner protective rubber 16i. At the outer end in the radial direction, the separation between the outer apex portion 8B and the clinch rubber 10 is suppressed.

  The edge cover rubber 15 and the inner and outer protective rubbers 16i and 16o are made of rubber having excellent adhesiveness. Specifically, natural rubber is used in an amount of 50% by mass or more as a rubber component, and adhesion such as rosin resin is applied. It is preferable to contain an agent. The complex elastic modulus E * 4 of the edge cover rubber 15 and the inner and outer protective rubbers 16i and 16o is preferably in the range of 5 to 13 MPa, and is set at least smaller than the complex elastic modulus E * 3 of the clinch rubber 10.

  In this example, a thin protective rubber portion 8B1 is formed on the outer apex portion 8B so as to face the inner protective rubber 16i, and the outer end of the ply folded portion 6b is formed between the outer apex portion 8B and the inner protective rubber 16i. 6E is sandwiched and protected. The protective rubber portion 8B1 is preferably formed with the same composition as the protective rubber 16i.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

  A heavy-duty tire (size 11.00R20) having the basic structure of FIG. 1 was prototyped based on the specifications in Table 1, and the bead durability of each sample tire was tested. The specifications other than those listed in Table 1 are the same. The complex elastic modulus E * 1 of the inner apex is 50 Mpa, the complex elastic modulus E * 2 of the outer apex is 4.0 Mpa, and the complex elastic modulus E * 3 of the clinch rubber is 12 Mpa. It is said.

<Bead durability>
The test tire is run on the drum tester at a speed of 20 km / h under the conditions of a rim (20 × 8.00V), internal pressure (810 kPa) and longitudinal load (556.6 kN) until damage occurs to the bead part. The travel distance was measured and displayed as an index with the travel distance of the tire of Example 1 as 100. The larger the value, the better.

  As shown in the table, it can be confirmed that the tires of the examples have significantly improved bead durability compared to the tires of the comparative examples.

It is sectional drawing which shows one Example of the tire for heavy loads of this invention. It is sectional drawing which expands and shows a bead part. It is sectional drawing which expands and shows a bead part. It is sectional drawing which shows the bead part of the conventional tire.

Explanation of symbols

2 Tread portion 3 Side wall portion 4 Bead portion 5 Bead core 6 Carcass 6A Carcass ply 6a Ply main body portion 6b Ply folded portion 8 Bead apex rubber 8A Inner apex portion 8B Outer apex portion 8S Interface 9 Bead reinforcement layer 9A Bottom piece portion 9i Inner piece Part 9o Outer piece 10 Clinch rubber 10A Rising part BL Bead base line K Intersection P1 Vertex X1 First reference line X2 Second reference line X3 Third reference line

Claims (6)

A carcass made of a carcass ply in which a ply turn-up portion that is turned from the inner side to the outer side in the tire axial direction around the bead core is connected in series to both ends of the ply main body portion that extends from the tread portion through the sidewall portion to the bead core of the bead portion;
A bead apex rubber extending between the bead core and the tire radial direction through between the ply folded portion and the ply body portion;
An inner piece portion extending in the radial direction along the tire axial direction inner side surface of the ply body portion and an outer piece portion extending in the radial direction along the tire axial direction outer side surface of the ply folded portion are radially inward of the bead core. U-shaped bead reinforcement layer connected in series by a bottom piece passing through
And a heavy duty tire comprising clinch rubber for preventing rim displacement, which is disposed on the outer side in the tire axial direction of the outer piece portion and has a rising portion that forms the outer surface of the bead portion,
The bead apex rubber has a triangular cross-section rising from the bead core and a radially inner inner apex portion made of highly elastic rubber having a vertex on the tire axially outer surface of the ply main body portion, and the ply from the apex. It consists of the outer apex part which is connected to the inner apex part via a boundary surface extending inward in the radial direction toward the turned-up part and is made of rubber having a lower elasticity than the inner apex part.
The radial height HPi from the bead base line of the radially outer end of the inner piece portion of the bead reinforcement layer is larger than the radial height HN from the bead base line of the radially outer end of the ply turn-up portion,
And the radial height HEi from the bead base line of the apex of the inner apex portion is larger than the radial height HPi of the inner piece portion,
In addition, the tire axial direction line passing through the radially outer end of the outer piece portion of the bead reinforcing layer extends from the intersection where the ply folded portion intersects the tire axial direction inner side surface on a second reference line orthogonal to the ply main body portion. While setting the rubber thickness T2i of the inner apex portion to 10 to 25% of the maximum width Wc in the tire axial direction of the bead core,
The rubber thickness T2o of the outer apex portion on the second reference line extends from the radially outer end of the ply turn-up portion, and the total rubber of the bead apex rubber on the first reference line orthogonal to the ply main body portion. 70-100% of the thickness T1 ,
Each outer end of the bead reinforcement layer and the outer end of the inner piece are covered and protected by edge cover rubber,
Between the ply folded portion and the clinch rubber, an inner and outer protective rubber is interposed,
The inner protective rubber rises from an edge cover rubber that covers the outer piece portion, and terminates beyond the outer end of the ply folded portion outward in the radial direction.
The outer protective rubber is interposed between the outer piece portion and the clinch rubber at the radially inner end from the inner protective rubber, and is located at the outer apex portion at the radially outer end from the inner protective rubber. Between the rubber and clinch rubber,
The edge cover rubber and the inner and outer protective rubbers use natural rubber as a rubber component in an amount of 50% by mass or more, have a complex elastic modulus E * 4 in the range of 5 to 13 MPa, and have a complex elastic modulus E * 3 of clinch rubber. Heavy duty tire characterized by being smaller .
  The rubber thickness J3c of the clinch rubber on the third reference line extending from the radially outer end of the ply turn-up portion and orthogonal to the outer surface of the bead portion is outside the radial direction of the ply turn-up portion on the third reference line. The heavy duty tire according to claim 1, wherein the tire is 20 to 40% of the total rubber thickness J3 from the end to the outer surface of the bead portion. When the tire cross-sectional height is H, the radial height HN of the ply folded portion, the radial height HPi of the inner piece portion of the bead reinforcing layer, and the radial height HEi of the inner apex portion are: The heavy duty tire according to claim 1, wherein the following condition is satisfied.
0.15H ≦ HN ≦ 0.35H
0.16H ≦ HPi ≦ 0.36H
0.17H ≦ HEi ≦ 0.37H The rubber thickness T2i of the inner apex portion on the second reference line, the rubber thickness T2o of the outer apex portion, and the total rubber thickness T1 of the bead apex rubber on the first reference line satisfy the following conditions. The heavy duty tire according to any one of claims 1 to 3.
0.6Wc ≦ (T2i + T2o) ≦ 1.0Wc
0.6Wc ≦ T1 ≦ 1.0Wc
0.5Wc ≦ T2o ≦ 0.7Wc The heavy duty tire according to any one of claims 1 to 4, wherein the rubber thickness J3c and the total rubber thickness J3 of the clinch rubber on the third reference line satisfy the following conditions.
0.6Wc ≦ J3 ≦ 1.2Wc
0.15Wc ≦ J3c ≦ 0.6Wc   The radial height HC from the bead base line of the radially outer end of the clinch rubber is 0.2 to 0.4 times the cross-sectional height H of the tire. Heavy duty tire according to crab.

Images