JP4465978B2 - Heavy duty pneumatic radial tire - Google Patents

Description

この表１から判るように、実施例のタイヤは従来例に比べて初期接着性及び耐水接着性が優れ、その結果、ビード部の耐久性が優れていた。
【００２４】
【発明の効果】
以上説明したように本発明によれば、重荷重用空気入りラジアルタイヤにおいて、ビードコアの周囲に被覆されるカバーゴム層を、ビードコアの全周囲を覆うように配置し、ジエン系ゴム１００重量部に対して、５重量部以上の硫黄と、コバルト元素として０．０５〜０．５重量部の有機酸コバルト塩を配合したゴム組成物から構成したから、ビードコア近傍でのカーカスコードの接着性を十分に確保し、ビード部の耐久性を向上することができる。
【図面の簡単な説明】
【図１】本発明の実施形態からなる重荷重用空気入りラジアルタイヤを示す半断面図である。
【図２】本発明の実施形態からなる重荷重用空気入りラジアルタイヤのカーカス層を拡大して示す断面図である。
【図３】本発明の実施形態からなる重荷重用空気入りラジアルタイヤのビード部を拡大して示す断面図である。
【符号の説明】
１ トレッド部
２ サイドウォール部
３ ビード部
４ カーカス層
４ａ カーカスコード
４ｂ カーカスコートゴム層
５ ビードコア
５ａ ビードワイヤ
５ｂ インシュレーションゴム層
６ カバーゴム層
７ ビードフィラー
８ 補強層
９ ベルト層[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a heavy-duty pneumatic radial tire using a steel cord for a carcass layer. More specifically, the adhesion of the carcass cord in the vicinity of the bead core is sufficiently ensured, and the durability of the bead portion is improved. The present invention relates to a pneumatic radial tire for heavy loads.
[0002]
[Prior art]
Carcass layer consisting of a plurality of steel cords arranged in the tire radial direction between a pair of left and right bead parts, and the end of the carcass layer is wound around the bead core from the inside of the tire to the outside for heavy load In the radial tire, the rubber gauge between the bead core and the carcass layer tends to be greatly reduced due to the winding of the carcass layer in the molding process and the rubber flow at the initial stage of vulcanization. In particular, when the gauge of the coated rubber of the carcass layer decreases, not only the initial adhesion between the steel cord and the rubber decreases, but also the adhesion decreases due to moisture penetration during use and storage of the tire. When the water is invaded due to trauma, the deterioration of adhesiveness becomes more remarkable. In the worst case, starting from the poor adhesion part as described above, the reinforcing layer embedded in the bead part may be peeled off or the carcass cord may be broken. There was a problem that it dropped extremely.
[0003]
On the other hand, it has been proposed that the rubber gauge between the bead core and the carcass layer is set thick in an unvulcanized state (see, for example, Patent Document 1). However, when the rubber gauge between the bead core and the carcass layer is set thick, failures such as cord breakage due to the loss of the rubber gauge can be prevented, but the adhesion of the carcass cord near the bead core is improved. Since no effect was obtained, the durability of the bead portion was not always sufficient.
[0004]
[Patent Document 1]
[Patent Document 1] Japanese Patent Laid-Open No. 10-193928
[Problems to be solved by the invention]
An object of the present invention is to provide a heavy-duty pneumatic radial tire that can sufficiently secure the adhesion of a carcass cord in the vicinity of a bead core and can improve the durability of a bead portion.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, a heavy-duty pneumatic radial tire according to the present invention includes a carcass layer in which a plurality of steel cords are arranged in the tire radial direction between a pair of left and right bead portions, In a heavy-duty pneumatic radial tire in which an end is wound around the bead core from the inside to the outside of the tire and a cover rubber layer is coated around the bead core, the cover rubber layer is disposed so as to cover the entire circumference of the bead core. The rubber composition is composed of 5 parts by weight or more of sulfur and 0.05 to 0.5 parts by weight of an organic acid cobalt salt as a cobalt element with respect to 100 parts by weight of a diene rubber. To do.
[0007]
As a countermeasure against the above problems, the present inventors focused on a cover rubber layer coated around the bead core, and an adhesive compound containing a large amount of sulfur and an organic acid cobalt salt was added to this cover rubber layer. I used it. Thus, when an adhesive compound is used for the bead core cover rubber layer, even if a rubber flow occurs around the bead core, the carcass cord can be covered with the adhesive compound of both the carcass layer and the cover rubber layer. Therefore, the initial adhesion and water-resistant adhesion of the carcass cord in the vicinity of the bead core can be sufficiently ensured, and as a result, peeling of the reinforcing layer embedded in the bead portion and breakage of the carcass cord are prevented, and the bead is The durability of the part can be improved.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.
[0009]
FIG. 1 shows a heavy-duty pneumatic radial tire according to an embodiment of the present invention, FIG. 2 shows an enlarged carcass layer, and FIG. 3 shows an enlarged bead portion. In the figure, 1 is a tread portion, 2 is a sidewall portion, and 3 is a bead portion.
[0010]
As shown in FIG. 1, a carcass layer 4 in which a plurality of carcass cords are arranged in the tire radial direction is mounted between a pair of left and right bead portions 3 and 3, and the carcass layer 4 extends in the tire width direction. The end is wound around the bead core 5 from the inside of the tire to the outside. As shown in FIG. 2, the carcass layer 4 includes a carcass cord 4a and a carcass coat rubber layer 4b. A steel cord is used for the carcass cord 4a. In addition, an adhesive compound is used as the rubber composition of the carcass coat rubber layer 4b.
[0011]
As shown in FIG. 3, the bead core 5 has a structure in which at least one bead wire 5a coated with insulation rubber is wound in a layered manner, and an insulation rubber layer 5b is mainly formed between the wires. The bead core 5 including the bead wire 5 a and the insulation rubber layer 5 b is covered with a cover rubber layer 6. Therefore, the insulation rubber layer 5b, the cover rubber layer 6, and the carcass coat rubber layer 4b are interposed between the bead wire 5a and the carcass cord 4a.
[0012]
A bead filler 7 made of hard rubber is disposed on the outer periphery of the bead core 5. Further, a reinforcement layer 8 formed by aligning a plurality of reinforcement cords is embedded in the bead portion 3 so as to wrap the carcass layer 4. On the other hand, on the outer peripheral side of the carcass layer 4 in the tread portion 1, a plurality of belt layers 9 formed by arranging a plurality of reinforcing cords are embedded.
[0013]
The above-described cover rubber layer 6 is usually coated to enhance the binding property of the bead wire 5a. Here, the rubber composition of the cover rubber layer 6 is 5 parts by weight based on 100 parts by weight of the diene rubber. A rubber composition containing at least sulfur by weight and 0.05 to 0.5 parts by weight of an organic acid cobalt salt as a cobalt element is used. As the diene rubber, natural rubber or synthetic rubber such as butadiene rubber, isoprene rubber or styrene butadiene rubber can be used. As the organic acid cobalt salt, cobalt naphthenate, cobalt stearate, cobalt oleate and the like can be used. Furthermore, compounding agents such as carbon black, inorganic filler, oil, resin, anti-aging agent, and vulcanizing agent can be added to the rubber composition, and the compounding agent is not particularly limited.
[0014]
As long as the above regulations are satisfied, the composition of the cover rubber layer 6 and the composition of the carcass coat rubber layer 4b or the insulation rubber layer 5b may be the same. The thickness of the cover rubber layer 6 is preferably 0.3 to 2.0 mm in order to sufficiently obtain the effect of improving adhesiveness.
[0015]
Thus, even if a rubber flow occurs around the bead core 5 by using an adhesive compound containing a large amount of sulfur and an organic acid cobalt salt in the cover rubber layer 6, the carcass layer 4 and the cover rubber The carcass cord 4a can be covered with both adhesive compounds of the layer 6. That is, even if the carcass coat rubber layer 4b is detached from the carcass cord 4a due to the rubber flow, the cover rubber layer 6 is surely present there. Therefore, it is possible to sufficiently ensure the initial adhesiveness and water-resistant adhesiveness of the carcass cord 4a in the vicinity of the bead core 5. As a result, it is possible to prevent peeling of the reinforcing layer 8 embedded in the bead portion 4 and breakage of the carcass cord 4a, thereby improving the durability of the bead portion.
[0016]
Here, in the rubber composition of the cover rubber layer 6, when the compounding amount of sulfur with respect to 100 parts by weight of the diene rubber is less than 5 parts by weight, the effect of improving the initial adhesiveness of the carcass cord 4a becomes insufficient. However, the upper limit of the amount of sulfur is desirably 35 parts by weight. Further, in the rubber composition of the cover rubber layer 6, when the compounding amount of the organic acid cobalt salt with respect to 100 parts by weight of the diene rubber is less than 0.05 parts by weight as a cobalt element, the effect of improving the initial adhesiveness and water resistant adhesiveness However, if it exceeds 0.5 parts by weight, the adhesiveness is rather deteriorated.
[0017]
By the way, if the carcass coat rubber layer 4b is thickened, it is possible to improve the initial adhesion and water-resistant adhesion of the carcass cord 4a. However, partially thickening the carcass coat rubber layer 4b is difficult in manufacturing, and increasing the thickness of the carcass coat rubber layer 4b over the entire tire causes an increase in weight. On the other hand, if an adhesive compound is employed for the cover rubber layer 6 as described above, the initial adhesion and water-resistant adhesion of the carcass cord 4a can be improved without causing an increase in weight.
[0018]
【Example】
Conventional examples, examples and comparative examples 1 to 3 in which the composition of the cover rubber layer covering the periphery of the bead core is varied as shown in Table 1 in the heavy-duty pneumatic radial tire having the rib pattern of the tire size 11R22.5 Were made respectively.
[0019]
These test tires were evaluated for initial adhesion, water-resistant adhesion, and bead durability by the following test methods, and the results are also shown in Table 1.
[0020]
Initial adhesion:
In accordance with ASTM D2229, a sample made of a steel cord and a rubber composition of a cover rubber layer was produced under the conditions of a temperature of 170 ° C. and a vulcanization time of 20 minutes. The rubber coverage (%) was measured. The evaluation results are shown as an index with the conventional example being 100. The larger the index value, the better the initial adhesiveness.
[0021]
Water-resistant adhesion:
In accordance with ASTM D2229, a sample comprising a steel cord and a rubber composition of a cover rubber layer was prepared under conditions of a temperature of 170 ° C. and a vulcanization time of 20 minutes, and this sample was immersed in warm water at a temperature of 70 ° C. for 4 weeks. After that, a cord pull-out test was performed, and the rubber coverage (%) in the drawn cord was measured. The evaluation results are shown as an index with the conventional example being 100. It means that water resistance adhesiveness is excellent, so that this index value is large.
[0022]
Durability of bead part:
The test tire is assembled on a rim with a rim size of 22.5 × 7.50 and inflated at an air pressure of 0.94 MPa. Was measured. The evaluation results are shown as an index with the conventional example being 100. It means that durability of a bead part is excellent, so that this index value is large. However, this test was performed only for the conventional example and the example.
[0023]
[Table 1]

As can be seen from Table 1, the tires of the examples had excellent initial adhesion and water-resistant adhesion as compared with the conventional examples, and as a result, the durability of the bead portion was excellent.
[0024]
【The invention's effect】
As described above, according to the present invention, in the heavy-duty pneumatic radial tire, the cover rubber layer that covers the periphery of the bead core is disposed so as to cover the entire periphery of the bead core, and is based on 100 parts by weight of the diene rubber. The rubber composition is composed of 5 parts by weight or more of sulfur and 0.05 to 0.5 parts by weight of an organic acid cobalt salt as a cobalt element, so that the adhesion of the carcass cord near the bead core is sufficient. Securing the durability of the bead portion.
[Brief description of the drawings]
FIG. 1 is a half sectional view showing a heavy-duty pneumatic radial tire according to an embodiment of the present invention.
FIG. 2 is an enlarged cross-sectional view showing a carcass layer of a heavy duty pneumatic radial tire according to an embodiment of the present invention.
FIG. 3 is an enlarged cross-sectional view of a bead portion of a heavy duty pneumatic radial tire according to an embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass layer 4a Carcass cord 4b Carcass coat rubber layer 5 Bead core 5a Bead wire 5b Insulation rubber layer 6 Cover rubber layer 7 Bead filler 8 Reinforcement layer 9 Belt layer

Claims (2)

A carcass layer in which a plurality of steel cords are arranged in the tire radial direction is mounted between a pair of left and right bead portions, and an end portion of the carcass layer is wound around the bead core from the inside of the tire to the outside. In a heavy-duty pneumatic radial tire covered with a cover rubber layer, the cover rubber layer is disposed so as to cover the entire periphery of the bead core , and 5 parts by weight or more of sulfur with respect to 100 parts by weight of the diene rubber. And a heavy-duty pneumatic radial tire composed of a rubber composition containing 0.05 to 0.5 parts by weight of an organic acid cobalt salt as a cobalt element. The heavy-duty pneumatic radial tire according to claim 1, wherein the composition of the cover rubber layer is the same as that of the carcass coat rubber layer of the carcass layer or the insulation rubber layer of the bead core.

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