JP2004231057A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of improving durability of a bead part on a basis of improving the structure of the bead part. <P>SOLUTION: The pneumatic tire 1 is equipped with a bead reinforced layer 9 consisting of carcass 6 containing a carcass ply 6A integrally having a main body part 6a and a clinch part 6b, a bead apex 8 disposed between the main body part 6a and the clinch part 6b, and a ply using a nylon cord disposed at the outside of the clinch part 6b. The bead apex 8 has JIS hardness of 75 to 85°and the height H1 of 60 to 85% of the tire maximum width height Hm. The bead reinforced layer 9 has the height H2 of an inner edge 9i of not more than 20% of the tire maximum width height Hm and the height H3 of an outer edge 9o of 30 to 85% of the tire maximum width height Hm. The outside of the bead reinforced layer 9 is covered with a clinch apex 10 made of a hard rubber. The rubber thickness t1 between the carcass cord of the main body part 6a and the inside surface of the bead apex 8, the rubber thickness t2 between the nylon cord of the bead reinforced layer 9 and the clinch apex 10, and the rubber thickness t3 between the carcass cord of the clinch part 6b and the nylon cord of the bead reinforced layer 9, are set to be not less than 0.8 mm respectively. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００２９】
テストの結果、実施例１、２は、耐久試験を合格しており、比較例に比べてビード部の耐久性が明らかに向上していることが確認できる。
【００３０】
【発明の効果】
以上説明したように、本発明の空気入りタイヤは、ビード部の構造を適切に改善したことにより、該ビード部の耐久性を向上しうる。
【図面の簡単な説明】
【図１】本発明の一実施形態を示す空気入りタイヤの断面図である。
【図２】そのビード部の部分拡大図である。
【図３】図２のＡ−Ｂ部拡大図である。
【符号の説明】
１ 空気入りタイヤ
２ トレッド部
３ サイドウォール部
４ ビード部
５ ビードコア
６ カーカス
６Ａ カーカスプライ
６ａ カーカスプライの本体部
６ｂ カーカスプライの折返し部
６ｃ カーカスコード
７ ベルト層
８ ビードエーペックスゴム
９ ビード補強層
９ｉ 内端
９ｏ 外端
９ｃ ナイロンコード
１０ クリンチエーペックス
Ｈｍ タイヤ最大幅高さ
Ｍ タイヤ最大幅位置[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a pneumatic tire that can enhance the durability of a bead portion and is suitable for, for example, a small truck.
[0002]
[Prior art]
For example, in a pneumatic tire for a small truck used under severe conditions with a large applied load, a large repeated strain acts on the bead portion. Therefore, damage is likely to occur near the bead portion. Conventionally, attempts have been made to arrange a bead reinforcing layer or the like using a reinforcing ply such as a nylon cord on the outside of the carcass of the bead portion to increase the bending rigidity of the bead portion, reduce distortion, and improve durability. (For example, see Patent Documents 1 to 3).
[0003]
[Patent Document 1]
JP-A-10-17720 [Patent Document 2]
JP 2001-277823 A [Patent Document 3]
JP-A-6-262913
[Problems to be solved by the invention]
The present inventors have conducted various experiments and found that the addition of the above-described bead reinforcing layer to the tire may unexpectedly lower the durability. Especially the inner end of the bead reinforcing layer, the height position of the outer end and the rubber thickness between the reinforcing cord and the carcass cord, and also the rubber thickness between the reinforcing cord and the clinch apex are not properly defined. Then, the stress generated in the tire itself, the shear strain between cords, and the like become larger than those in the related art.
[0005]
The present invention has been devised in view of the above problems, and provides a pneumatic tire capable of improving the durability of a bead portion based on improving the structure of the bead portion as described above. It is aimed at.
[0006]
[Means for Solving the Problems]
The invention according to claim 1 of the present invention integrates a main body portion extending from the tread portion to the bead core of the bead portion via the sidewall portion, and a folded portion which is folded around the bead core from the inside in the tire axial direction to the outside. The carcass ply having a carcass ply, a bead apex disposed between the main body portion and the folded portion of the carcass ply, and extending from an outer surface of the bead core in a radially outward direction in a tire radial direction, and an axial direction of the folded portion of the carcass ply. A pneumatic tire provided with a bead reinforcing layer made of a ply using a reinforcing cord arranged on the outside, wherein the bead apex has a JIS hardness of 75 to 85 mm and a height from a bead base line of the tire. The bead reinforcing layer has a height at the inner end in the tire radial direction of which is a maximum width of the tire. 20% or less of the height of the tire in the radial direction of the tire and 30 to 85% of the maximum width of the tire, and the outside of the bead reinforcing layer in the tire axial direction is covered with a clinch apex made of hard rubber. And a rubber thickness t1 between the carcass cord of the main body portion of the carcass ply and the inner surface of the bead apex in the tire axial direction, and a rubber thickness between the reinforcing cord of the bead reinforcing layer and the clinch apex. It is characterized in that both t2 and a rubber thickness t3 between the carcass cord of the folded portion of the carcass ply and the reinforcing cord of the bead reinforcing layer are 0.8 mm or more.
[0007]
The invention according to claim 2 is the pneumatic tire according to claim 1, wherein the carcass ply has a carbon dispersion rate of a topping rubber covering the carcass cord of 90% or more.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 shows a tire meridian sectional view including a tire axis of the pneumatic tire of the present embodiment. Note that this state is a normal state with no load in which the tire is assembled on a normal rim (not shown) and filled with a normal internal pressure.
[0009]
The "regular rim" is a rim defined for each tire in a standard system including a standard on which the tire is based. For example, a standard rim for JATMA, a "Design Rim" for TRA, or an ETRTO In that case, “Measuring Rim” is set. The "normal internal pressure" is the air pressure defined for each tire in the standard system including the standard on which the tire is based. For JATMA, the maximum air pressure is used. For TRA, the table "TIRE LOAD LIMITS" is used. The maximum value described in AT VARIOUS COLD INFLATION PRESSURES ”is set to“ INFLASION PRESSURE ”for ETRTO, but is set to 180 kPa when the tire is for a passenger car. In the following, unless otherwise specified, the dimensions and the like of each part of the tire are specified in this normal state.
[0010]
In the figure, the pneumatic tire of the present embodiment is folded back from the tread portion 2 to the bead core 5 of the bead portion 4 via the sidewall portion 3 to the bead core 5, and from the inside in the tire axial direction to the outside around the bead core 5. A carcass 6 including a carcass ply 6A integrally having a folded portion 6b, a belt layer 7 disposed outside the carcass 6 in the tire radial direction and inside the tread portion 2, a main body 6a and a folded portion 6b of the carcass ply 6A. In this example, a nylon cord 9c (as a reinforcement cord) is disposed between the bead apex 8 and the folded portion 6b of the carcass ply 6A. 3 (shown in FIG. 3) for a small truck having a bead reinforcing layer 9 made of a ply.
[0011]
The carcass 6 has at least one carcass cord having a radial structure in which carcass cords are arranged at an angle of, for example, 75 ° to 90 ° with respect to the tire equator C. In this example, three carcass plies 6A1, 6A2, and 6A3 (when collectively referred to as Simply referred to as a carcass ply 6A). As shown in FIG. 3, each carcass ply 6A is made of a cord ply in which both sides of a carcass cord 6c substantially aligned in parallel are covered with topping rubber 6g. In the present embodiment, a polyester cord is used for the carcass cord 6c. However, other than this, an organic fiber cord such as nylon, rayon, and aramid can be adopted.
[0012]
In addition, the carcass 6 of this example exemplifies a carcass ply 6A in which all three carcass plies 6A are formed by a so-called folded ply having a main body 6a and a folded portion 6b. The heights hc1, hc2, and hc3 of the folded portions 6b of the plies 6A1, 6A2, and 6A3 from the bead base line BL are not particularly limited, but are 30 to 50%, 40 to 60%, and 30%, respectively, of the tire section height H. It is good to set to about 70 to 80%.
[0013]
As described above, in the carcass ply 6A, the height of each folded portion 6b is shifted (hc1 ≠ hc2 ≠ hc3), thereby preventing a large rigidity step from being generated in the sidewall portion 3. Also, by terminating at a higher position as the carcass ply is located on the outer side of the folded portion 6b (hc3>hc2> hc1), the end of the inner folded portion can be covered. This is useful for suppressing separation or the like at the end of the folded portion 6b. In the pneumatic tire 1 of the present invention, the carcass 6 only needs to include at least one folded ply, and it goes without saying that the ply configuration and the like can be appropriately changed.
[0014]
The belt layer 7 is composed of at least two belt cords arranged with a belt cord inclined at a small angle of, for example, 10 to 45 ° with respect to the tire equator, and in this example, three belt plies 7A and 7B overlapping inside and outside in the tire radial direction. And 7C are superposed in a direction in which the cords cross each other. The middle belt ply 7B located in the middle in the tire radial direction is formed wider than the inner and outer belt plies 7A and 7C, and prevents the occurrence of a rigid step due to the overlapping ends of the respective plies. . As the belt cord, a steel cord is employed in this example. However, a highly elastic organic fiber cord such as aramid or rayon can be used as needed.
[0015]
The bead apex rubber 8 is made of a rubber material having a JIS hardness of 75 to 85 °. The JIS hardness is a durometer type A based on JIS-K6253. If the JIS hardness of the bead apex rubber 8 is less than 75 °, the durability of the bead portion and the steering stability tend to be reduced due to insufficient rigidity. As a result, the stress cannot be relieved and the durability also decreases. Particularly preferably, the JIS hardness is set to 78 to 82 °.
[0016]
The height h1 of the bead apex rubber 8 from the bead base line BL is set to 60 to 85% of the tire maximum width height Hm. The tire maximum width height Hm is the height from the bead base line BL at the tire maximum width position M that forms the largest width SW excluding the height of the sidewall portion 3 in the normal state, excluding the height of the pattern, characters, and the like. When the height h1 of the bead apex rubber 8 is less than 60% of the maximum width Hm of the tire, the rigidity of the bead portion 4 is insufficient, the durability is reduced, and the steering stability is liable to be deteriorated. If it exceeds 85%, the rigidity of the bead portion 4 is excessively increased, so that the stress cannot be reduced and the durability is reduced. Particularly preferably, the height h1 is desirably 70 to 80% of the tire maximum width height Hm.
[0017]
The tire maximum width Hm itself is not particularly limited, but is preferably set to about 40 to 60% of the tire section height H.
[0018]
As shown in FIGS. 2 and 3, the bead reinforcing layer 9 is made of a cord ply of a small thickness in which both sides of a nylon cord 9c aligned in parallel are covered with topping rubber 9g. Are composed of inner and outer plies 9A and 9B. The number of plies is not particularly limited, but is preferably about 1 or 2 sheets, and particularly preferably 2 sheets as in the present embodiment. The bead reinforcing layer 9 is disposed at the bead portion 4 and outside the folded portion 6b of the carcass ply 6A in the tire axial direction. The reinforcing cord is preferably an organic fiber cord, preferably a nylon cord, but other organic fiber cords such as polyester and rayon can be used.
[0019]
The height h2 of the inner end 9i in the tire radial direction of the bead reinforcing layer 9 is set to 20% or less of the tire maximum width height Hm. Thereby, the inner end 9i of the bead reinforcing layer 9 can be firmly held between the flange of the rim (not shown) and the bead core 5, and the inner end 9i can be reliably prevented from becoming a starting point of damage.
[0020]
In the bead reinforcing layer 9, the height h3 of the outer end 9o in the tire radial direction is set to 30 to 85% of the tire maximum width height Hm. If the height h3 is less than 30% of the maximum tire width Hm, the rigidity of the bead portion 4 tends to be insufficient, and the durability tends to be insufficiently improved. Since the outer end 9o approaches the tire maximum width position M where the bending is severe, the outer end 9o easily becomes a starting point of damage such as separation. Particularly preferably, the height h3 is desirably 60 to 80% of the tire maximum width height Hm.
[0021]
In the bead reinforcing layer 9 of the present embodiment, the inner and outer plies 9A and 9B have the same height on the inner end 9i side, and have different heights on the outer end 9o side, and the outer ply 9B has bead reinforcement. The aspect which comprises the outer end 9o of the layer 9 is shown. This enhances the reinforcing effect on the inner end 9i side of the bead reinforcing layer 9 that is unlikely to be a starting point of damage. On the other hand, the outer end of the inner ply 9A is covered with the outer ply 9B. This helps to prevent the outer end from becoming a source of damage.
[0022]
The outside of the bead reinforcing layer 9 in the tire axial direction is covered with a clinch apex 10 made of hard rubber. The clinch apex 10 of the present example is configured such that the outer end 10a in the tire radial direction is smaller in height than the outer end 9o of the bead reinforcing layer 9, and covers substantially 60% or more of the bead reinforcing layer 9. Have been. Such clinch apex 10 forms the outer surface of the bead portion that contacts at least the flange of the rim. Therefore, it is made of a hard rubber material having excellent wear resistance. The rubber material preferably has a JIS hardness of 60 to 80 °, more preferably 65 to 75 °. When the JIS hardness is less than 60 °, rim misalignment and durability are liable to occur. Conversely, when the JIS hardness exceeds 80 °, rim assemblability is deteriorated, rubber cracks or rubber chips are likely to occur, which is preferable. Absent.
[0023]
Further, the pneumatic tire 1 of the present invention, as shown in an enlarged manner in FIG. 3, has a structure in which the outermost carcass cord 6c of the main body 6a of the carcass ply 6A and the inner side surface 8i of the bead apex 8 in the tire axial direction. The rubber thickness t1, the rubber thickness t2 between the outermost nylon cord 9c of the bead reinforcing layer 9 and the clinch apex 10, and the outermost carcass cord 6c of the folded portion 6b of the carcass ply 6A and the bead reinforcing layer 9 The rubber thickness t3 between the outermost nylon cord 9c and the outermost nylon cord 9c is set to 0.8 mm or more.
[0024]
When the thicknesses t1, t2, and t3 are less than 0.8 mm, touching between cords (that is, direct contact between cords or cords and members other than topping rubber) occurs, or shearing force increases. Therefore, damage is likely to occur starting from this portion. Particularly preferably, the thicknesses t1, t2 and t3 are desirably 0.8 to 1.0 mm, more preferably 0.9 to 1.0 mm. Such adjustment of the thickness can be performed by changing the thickness of the topping rubber of each ply, or by separately interposing a new rubber sheet.
[0025]
In a particularly preferred embodiment, the carbon dispersion of the topping rubber 6g covering the carcass cord 6c of the carcass ply 6A is preferably 90% or more. If the carbon dispersion rate is less than 90%, cracks tend to occur in the topping rubber 6g of the carcass ply 6A passing through the bead portion, starting from the interface between the mass of carbon particles and the rubber.
[0026]
The carbon dispersion ratio (also referred to as carbon black dispersion degree) decreases as the dispersion becomes worse, assuming that the state where carbon is completely dispersed in the rubber is 100%. Specifically, it is calculated by measuring the amount of carbon that is not dispersed per unit area of rubber, and in this specification, it is measured by the ASTM D2663B method using an optical microscope. As a method for setting the carbon dispersion ratio in the above-described range, a method of surely performing a rubber kneading step and mixing a dispersant may be mentioned.
[0027]
【Example】
A pneumatic tire for a small truck having a tire size of 195 / 85R16 was prototyped according to the specifications in Table 1, and a durability test was performed to compare the performance. In the durability test, the tire was assembled on a rim (16 × 5.5K) and filled with an internal pressure of 600 kPa, and a vertical load of about 2.3 times (26.6 KN) the maximum load of the JATMA standard was applied, and the speed was 20 km. If the vehicle can run on the drum at / H and run for 300 hours without any visual destruction, the test is passed. In the case of rejects, the time at which damage occurred is indicated by an index with the example taken as 100.
Table 1 shows the test results and the like.
[0028]
[Table 1]

[0029]
As a result of the test, Examples 1 and 2 passed the durability test, and it can be confirmed that the durability of the bead portion was clearly improved as compared with the comparative example.
[0030]
【The invention's effect】
As described above, the pneumatic tire of the present invention can improve the durability of the bead portion by appropriately improving the structure of the bead portion.
[Brief description of the drawings]
FIG. 1 is a sectional view of a pneumatic tire showing one embodiment of the present invention.
FIG. 2 is a partially enlarged view of the bead portion.
FIG. 3 is an enlarged view of a portion AB in FIG. 2;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 6A Carcass ply 6a Carcass ply main part 6b Carcass ply turnup part 6c Carcass cord 7 Belt layer 8 Bead apex rubber 9 Bead reinforcement layer 9i Inner end 9o Outer end 9c Nylon cord 10 Clinch apex Hm Tire maximum width Height M Tire maximum width position

Claims (2)

A carcass including a carcass ply having a body portion extending from a tread portion to a bead core of a bead portion via a sidewall portion, and a folded portion integrally folded from the inside in the tire axial direction to the outside around the bead core,
A bead apex disposed between the main body portion and the folded portion of the carcass ply and tapered outward in the tire radial direction from the outer surface of the bead core, and a reinforcing cord disposed axially outside the folded portion of the carcass ply. A pneumatic tire having a bead reinforcing layer made of a ply used,
The bead apex has a JIS hardness of 75 to 85 mm and a height from a bead baseline of 60 to 85% of a tire maximum width height,
In the bead reinforcing layer, the height of the inner end in the tire radial direction is 20% or less of the tire maximum width height, and the height of the outer end in the tire radial direction forms 30 to 85% of the tire maximum width height. In addition, the outside of the bead reinforcing layer in the tire axial direction is covered with a clinch apex made of hard rubber,
The rubber thickness t1 between the carcass cord of the body portion of the carcass ply and the inner surface of the bead apex in the tire axial direction, the rubber thickness t2 between the reinforcing cord of the bead reinforcing layer and the clinch apex, and A pneumatic tire, wherein a rubber thickness t3 between a carcass cord at a folded portion of the carcass ply and a reinforcing cord of the bead reinforcing layer is 0.8 mm or more. The pneumatic tire according to claim 1, wherein the carcass ply has a carbon dispersion of a topping rubber covering the carcass cord of 90% or more.

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