JP4477755B2 - Heavy duty radial tire - Google Patents

Description

【００４１】
表１の如く、実施例品は、ビード耐久性を維持しながら耐トウ欠け性を大巾に向上しているのが確認できる。なお比較例１では、インスレーションゴム層とチェーファとの接着性はまだ保たれ、補強コードフィラに達する亀裂には至らないが、カーカスの折返し端での緩衝性が減じ、耐久性が低下した。
【００４２】
【発明の効果】
叙上の如く本発明は構成しているため、ビード耐久性を損ねることなくトウ欠けを効果的に抑制しうる。
。
【図面の簡単な説明】
【図１】本発明の一実施例のタイヤの断面図である。
【図２】そのビード部を拡大して示す断面図である。
【図３】（Ａ）、（Ｂ）は、従来のビード構造を説明する断面図である。
【図４】（Ａ）〜（Ｃ）は、従来技術の問題点を説明する線図である。
【符号の説明】
２ トレッド部
３ サイドウォール部
４ ビード部
４ｔ ビードトウ部分
５ ビードコア
６ カーカス
６ａ 本体部
６ｂ 折返し部
７ インナーライナ
７Ｓ インナーライナの内側面
９ チェーファ、
９Ｓ 終端面
１０ インスレーションゴム層、
１５ インナーサイドウォールゴム層、
１６ トウ内側ゴム層
１７ ゴムストリップ層
Ｓ１ ビード底面
Ｓ２ ビード外側面[0001]
BACKGROUND OF THE INVENTION
The present invention is particularly suitable for trucks and buses, and relates to a heavy duty radial tire capable of suppressing rubber chipping (tow chipping) in a bead toe portion when rim assembly and rim removal while maintaining bead durability.
[0002]
[Prior art]
Since heavy duty radial tires for trucks and buses are used under high internal pressure and high load, the bead portion comes into contact with the rim with a very high fitting pressure. For this purpose, as shown in FIG. 3 (A), the bead portion a has a chafer b made of hard rubber forming a rubber outer shell in a contact area with the rim from the toe portion at, through the heel portion ah to the bead outer surface ao. Is provided.
[0003]
The chafer b generally has a structure having an upright piece b1 that covers the inner end c1 of the air-impermeable inner liner rubber c and rises radially outward in the toe portion at (for convenience, a covering structure). Is widely adopted. This is because the adhesiveness of the inner liner rubber c to the molding former is high. As shown in FIG. 3B, the inner end c1 of the inner liner rubber c is exposed at the tire cavity surface. When a structure (referred to as an exposed structure for convenience) is adopted, the inner end c1 of the inner liner rubber c tends to peel off from the chafer b when the green tire is removed from the molding former. This is because production efficiency is impaired because it takes time to remove the green tires. From such a viewpoint, the covering structure is widely adopted.
[0004]
[Problems to be solved by the invention]
However, in the tire, when assembling / removing the rim, the toe portion at is caught by the rim flange rf and deformed as shown in FIGS. 4 (A) and 4 (B). The maximum elongation acts on the hard standing piece b1 on the tire cavity surface side. As a result, in the vicinity of the height position of the radially inner end of the bead core e, the standing piece b1 has a toe such as crack damage. Chips k are likely to occur.
[0005]
Further, since the chafer b has a high modulus rubber blending, the orientation at the time of extrusion molding is strong and the adhesiveness is poor. Therefore, as shown in FIG. 4 (C), when cracks easily progress from the toe-missed portion along the interface bs of the chafer b and reach the reinforcing cord filler j (carcass when there is no reinforcing cord filler j), There is also a risk of tying up cords from rust and bursting tires.
[0006]
Accordingly, the present invention impairs bead durability on the basis of the formation of an inner rubber layer having a predetermined rubber property that has a low rubber hardness and a high elongation at break instead of the standing piece portion in the tire having the covering structure. An object of the present invention is to provide a heavy duty radial tire that can effectively suppress toe chipping.
[0007]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, the invention of claim 1 of the present application has a folded portion that folds back from the inner side to the outer side in the tire axial direction around the bead core in the main body portion extending from the tread portion through the sidewall portion to the bead core of the bead portion. A heavy-duty radial tire comprising a series of carcass and an inner liner made of an air-impermeable rubber material that forms a tire lumen surface,
An insulation rubber layer extending inward and outward in the radial direction between the main body and the inner liner and having an inner end positioned below the bead core;
An inner sidewall rubber layer extending radially inward in the tire axial direction outside the folded portion and below the bead core;
A chafer which is arranged on the outer side in the tire axial direction of the inner sidewall rubber layer and reaches the bead toe portion and terminates to form a bead outer surface and a bead bottom surface,
And a toe inner rubber layer that is in contact with the end surface where the chafer terminates and extends in a radially outward direction along the tire axial direction inner surface of the inner liner,
The toe inner rubber layer is characterized by having a rubber hardness of 60 ° (durometer A hardness) or less and an elongation at break of 500% or more.
[0008]
In the invention according to claim 2, the rubber hardness is characterized in that the rubber hardness of each part is in the relationship of inner liner <toe inner rubber layer≈inner sidewall rubber layer <insulation rubber layer <chafer.
[0009]
According to a third aspect of the invention, the toe inner rubber layer is continuous with the inner sidewall rubber layer.
[0010]
According to a fourth aspect of the invention, the inner sidewall rubber layer is in contact with the lower surface of the insulation rubber layer below the bead core.
[0011]
According to a fifth aspect of the present invention, there is provided a rubber strip layer having a rubber hardness 15 to 25 ° greater than the rubber hardness of the inner sidewall rubber layer between the folded portion and the inner sidewall rubber layer. It is a feature.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 illustrates a meridional section when the heavy duty radial tire of the present invention is formed as a truck / bus tire.
[0013]
In the figure, a heavy-duty radial tire 1 (hereinafter referred to as a tire 1) includes a carcass 6 that is folded and locked by a bead core 5 of a bead portion 4 through a sidewall portion 3 from a tread portion 2 and a tire lumen surface. An inner liner 7 is provided.
[0014]
The carcass 6 is provided with one or more, in this example, one sheet of folded-back portions 6b that fold around the bead core 5 from the inner side to the outer side in the tire axial direction at both ends of the body part 6a straddling the bead cores 5 and 5. The thing formed from the carcass ply 6A is illustrated. This carcass ply 6A has a so-called radial structure in which carcass cords are arranged at an angle of 70 to 90 ° with respect to the tire equator C. As a carcass cord, an organic fiber cord such as nylon, rayon, polyester, aromatic polyamide, or steel is used. A cord is preferably used.
[0015]
A belt layer 11 is disposed outside the main body portion 6a of the carcass 6 and inside the tread portion 2. In this example, the belt layer 11 includes an innermost belt ply 11A in which belt cords using steel cords are arranged at an angle of, for example, about 60 ± 10 ° with respect to the tire equator C, and 30 with respect to the tire equator C. The belt plies 11B, 11C, and 11D are arranged at a small angle of less than 0 °, and for example, one or more places where the belt cords cross each other between the plies are provided and overlapped. As the belt cord, an organic fiber cord such as nylon, polyester, rayon, aromatic polyamide or the like can be used as necessary.
[0016]
A bead apex rubber 12 is provided between the main body portion 6a and the turn-up portion 6b of the carcass 6 so as to taper outward from the bead core 5 in the radial direction. The bead core 5 has, for example, a ring shape formed by winding a steel bead wire. In this example, the bead core 5 is a flat hexagon having a horizontally long cross section, and its radially inner side 5S is substantially parallel to the bead bottom surface S1. By extending, the fitting force with the rim is increased over a wide range.
[0017]
An inner liner 7 that forms substantially the entire tire cavity surface is disposed inside the main body 6 a of the carcass 6 via an insulation rubber layer 10. The inner liner 7 is made of an air-impermeable rubber mainly composed of, for example, butyl rubber, and its radially inner end 7E has a radially inner end of the bead core 5 as shown in FIG. It terminates radially inward from the reference line X passing in the axial direction. Thereby, the filling air is kept airtight.
[0018]
The insulation rubber layer 10 is a high-adhesion rubber that is interposed between the inner liner 7 and the main body 6a and extends inward and outward in the radial direction to increase the adhesive force between them. Natural rubber is preferably used. used. The inner end portion 10E of the insulation rubber layer 10 is located below the bead core 5. Specifically, the inner end portion 10E extends from the inner end 7E of the inner liner 7 and to the carcass 6 below the bead core. It has a substantially straight lower surface 10S that contacts (or intersects) and terminates.
[0019]
In this example, a preferable case is provided in which a reinforcing cord filler 13 is provided around the bead core 5 so as to wrap around the bead core 5 so as to wrap around the body portion 6a and the folded portion 6b. ing. The reinforcing cord filler 13 is made of, for example, a ply in which steel cords or organic fiber cords are juxtaposed, and reinforces the bead portion 4 and improves bead rigidity.
[0020]
Accordingly, in this example, the lower surface 10S is formed in a substantially linear shape that contacts (or intersects) the reinforcing cord filler 13 under the bead core. As in this example, it is preferable to form the lower surface 10S substantially parallel to the inner side 5S of the bead core 5 in order to stabilize the compression under the bead core.
[0021]
In the tire 1 of the present application, the bead portion 4 is further provided with an inner sidewall rubber layer 15, a chafer 9, and a toe inner rubber layer 16.
[0022]
The inner side wall rubber layer 15 is mainly intended to buffer the distortion between the folded portion 6b and the outer winding portion 13o of the reinforcing cord filler 13 and the chafer 9, for example, rubber hardness A soft rubber having an angle of 57 ° ± 3 ° is preferably used.
[0023]
In addition, "rubber hardness" said by this application means the durometer A hardness measured by durometer type A based on JIS-K6253.
[0024]
The inner sidewall rubber layer 15 extends outward in the tire axial direction of the folded portion 6b and inward in the tire radial direction and below the bead core 5. Specifically, the inner sidewall rubber layer 15 includes a main portion 15A that covers the folded portion 6b and the outer roll-up portion 13o and extends radially inward to the bead heel portion 4h, and is connected to the main portion 15A and below the bead core 5. Comprises a thin sub-portion 15B extending in contact with the lower surface 10S of the insulation rubber layer 10. The sub portion 15B is in contact with the reinforcing cord filler 13 on the outer side in the tire axial direction from the lower surface 10S.
[0025]
The sub-portion 15B improves mutual adhesive strength by buffering distortion between the insulation rubber layer 10 and the reinforcing cord filler 13 (the carcass 6 when the reinforcing cord filler 13 is not provided) and the chafer 9. , The progress of cracks along the interface of the chafer 9 is suppressed. However, the rubber thickness of the sub-portion 15B is preferably 1.0 mm or less. If it exceeds 1.0 mm, the fitting force with the rim is reduced, and the chafer itself has a lack of rubber thickness. There is a risk of causing crack damage to the chafer 9.
[0026]
The main portion 15A extends radially outward beyond the winding end of the outer winding portion 13o and the folding end of the folding portion 6b. In this example, the main portion 15A is in contact with the outer side surface of the bead apex rubber 12 in the tire axial direction. is doing. The rubber thickness of the main portion 15A needs to be larger than the rubber thickness of the sub-portion 15B. Particularly, the thickness of 1 to 2 mm sufficiently exhibits the buffering effect, and the rolled-up end and the turn-up. It is preferable for preventing peeling damage at the edge.
[0027]
In this example, the rubber strip layer 17 is disposed between the inner sidewall rubber layer 15 and the folded portion 6b. This rubber strip layer 17 surrounds the outer winding portion 13o and the folded portion 6b and prevents its movement, thereby further suppressing peeling damage at the winding end and the folded end. Accordingly, the rubber strip layer 17 is preferably made of a hard rubber having a rubber hardness higher than that of the inner sidewall rubber layer 15 and particularly 15 to 25 ° larger than that of the inner sidewall rubber layer 15. The
[0028]
Next, the chafer 9 is made of hard rubber for preventing rim displacement that forms the rubber skin of the bead portion 4, and rises 9A that forms the bead outer surface S2, and the bead bottom surface S1 that is connected to the rise portion 9A. The base portion 9B is provided integrally. The rising portion 9A is disposed on the outer side in the tire axial direction of the inner sidewall rubber layer 15 and extends radially inward to the bead heel portion 4h. Further, the base portion 9B terminates by reaching the bead toe portion 4t through the bead heel portion 4h.
[0029]
The bead bottom surface S1 and the bead outer surface S2 formed by exposing the chafer 9 include at least a rim contact region where the bead portion 4 contacts the rim, thereby preventing damage due to rim displacement. The rising portion 9A is adjacent to the main portion 15A of the inner sidewall rubber layer 15, and the base portion 9B is adjacent to the sub portion 15B.
[0030]
Next, the toe inner rubber layer 16 is made of soft rubber for preventing toe chipping having a substantially triangular cross section, and comes into contact with the end surface 9S where the chafer 9 terminates, and from the end surface 9S to the inner liner 7. The tire extends along the tire axial direction inner surface 7S while gradually decreasing the thickness outward in the radial direction. In this example, the end face 9S is illustrated as a substantially straight line connecting the tip P of the bead toe portion 4t and the inner end 7E of the inner liner 7.
[0031]
Also, the radially outer end 16E of the toe inner rubber layer 16 terminates radially outward from the reference line X and on the tire cavity surface. The above-described covering structure covering the end 7E is configured. As a result, in the bead portion 4, the toe inner rubber layer 16, the inner liner 7, the insulation rubber layer 10, and the reinforcement cord are formed on the reference line X from the tire lumen surface to the bead core 5 toward the outer side in the tire axial direction. The filler 13 and the carcass 6 are arranged in this order.
[0032]
Further, in this example, the case where the toe inner rubber layer 16 is formed of an integral rubber continuous with the inner sidewall rubber layer 15 is illustrated. As a result, the efficiency of the extrusion molding and the tire formation on the former can be improved, and the productivity can be maintained.
[0033]
Next, in order to reliably achieve the effect of preventing toe chipping by the toe inner rubber layer 16, the rubber hardness of the toe inner rubber layer 16 is regulated to 60 ° or less and the elongation at break to 500% or more. is required. If the rubber hardness is greater than 60 ° or the elongation at break is less than 500%, the local strain concentrated under the reference line X cannot be followed when the rim is assembled / removed, and a tow chip tends to occur. Become.
[0034]
Note that forming the toe inner rubber layer 16 and the inner sidewall rubber layer 15 with the rubber having the same composition not only makes the extrusion more efficient, but also promotes the progress of cracks from the tow chip, In addition, it is more preferable for suppressing peeling damage at the folded end of the carcass 6.
[0035]
Here, the lower limit value of the rubber hardness of the toe inner rubber layer 16 needs to be larger than the rubber hardness of the inner liner 7 in order to obtain the advantages of the above-described covering structure. In particular, when considering good balance with durability, rim fitting property, etc., the rubber hardness of each part is preferably in the following relationship.
Inner liner <toe inner rubber layer ≒ inner side wall rubber layer <insulation rubber layer <chafer [0036]
The inner liner 7, the insulation rubber layer 10, and the chafer 9 are not particularly restricted, and those having a conventionally used rubber hardness can be suitably used. That is, a rubber having a rubber hardness of 45 ° ± 3 ° for the inner liner 7, 68 ° ± 3 ° for the insulation rubber layer 10, and 79 ° ± 3 ° for the chafer 9 is suitable.
[0037]
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.
[0038]
[Example 1]
A tire having a tire size of 11R22.5 and having the structure shown in FIGS. 1 and 2 was made on the basis of the specifications shown in Table 1, and the toe chipping and bead durability of each sample tire were measured. 1.
[0039]
(1) Toe chipping property: (Accelerated rim assembly test)
Using a rim assembly machine (hydraulic tire changer), a sample tire was assembled with a rim on an aluminum wheel rim of size 8.25 × 22.5, and inspected for the presence of toe chipping. In addition, the aluminum wheel rim used the thing which the tip of the flange was shaved and the bead toe part was easily caught when the flange was passed over. In addition, turning the tires as slowly as possible promoted damage when overcoming the flange.
(2) Tow chipping property: (road test)
At the end of the 1st life when the mileage was 100,000 km or more, the user removed the rim, and inspected for the presence of tow chipping.
(3) Bead durability:
Using a drum tester, it was run at an internal pressure (1000 kPa), load (5000 kgf), speed (20 km / h). it's shown. The greater the value, the better the durability.
[0040]
[Table 1]

[0041]
As shown in Table 1, it can be confirmed that the examples have greatly improved toe chip resistance while maintaining bead durability. In Comparative Example 1, the adhesion between the insulation rubber layer and the chafer was still maintained, and the crack reaching the reinforcing cord filler was not reached, but the buffering property at the folded end of the carcass was reduced and the durability was lowered.
[0042]
【The invention's effect】
Since the present invention is configured as described above, toe chipping can be effectively suppressed without impairing the bead durability.
.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a tire according to an embodiment of the present invention.
FIG. 2 is an enlarged cross-sectional view of the bead portion.
FIGS. 3A and 3B are cross-sectional views illustrating a conventional bead structure. FIGS.
FIGS. 4A to 4C are diagrams illustrating problems of the prior art.
[Explanation of symbols]
2 Tread part 3 Side wall part 4 Bead part 4t Bead toe part 5 Bead core 6 Carcass 6a Body part 6b Folding part 7 Inner liner 7S Inner side surface 9 of inner liner
9S end face 10 insulation rubber layer,
15 inner sidewall rubber layer,
16 Toe inner rubber layer 17 Rubber strip layer S1 Bead bottom surface S2 Bead outer surface

Claims (5)

A carcass with a series of folded parts that fold from the inner side to the outer side in the tire axial direction around the bead core on the main body part from the tread part to the bead core of the bead part, and forming a tire lumen surface and impervious to air A heavy-duty radial tire comprising an inner liner made of a conductive rubber material,
An insulation rubber layer extending inward and outward in the radial direction between the main body and the inner liner and having an inner end positioned below the bead core;
An inner sidewall rubber layer extending radially inward in the tire axial direction outside the folded portion and below the bead core;
A chafer which is arranged on the outer side in the tire axial direction of the inner sidewall rubber layer and reaches the bead toe portion and terminates to form a bead outer surface and a bead bottom surface,
And a toe inner rubber layer that is in contact with the end surface where the chafer terminates and extends in a radially outward direction along the tire axial direction inner surface of the inner liner,
The radial tire for heavy loads, wherein the toe inner rubber layer has a rubber hardness of 60 ° (durometer A hardness) or less and an elongation at break of 500% or more. The radial tire for heavy loads according to claim 1, wherein the rubber hardness of each part has the following relationship.
Inner liner <toe inner rubber layer ≒ inner side wall rubber layer <insulation rubber layer <chafer The radial tire for heavy loads according to claim 1, wherein the toe inner rubber layer is continuous with the inner sidewall rubber layer. The radial tire for heavy loads according to any one of claims 1 to 3, wherein the inner sidewall rubber layer is in contact with the lower surface of the insulation rubber layer below the bead core. 5. A rubber strip layer having a rubber hardness 15 to 25 degrees larger than the rubber hardness of the inner sidewall rubber layer is interposed between the folded portion and the inner sidewall rubber layer. A heavy-duty radial tire according to any one of the above.

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