JP4291537B2 - Pneumatic tire - Google Patents

Description

【００４２】
【表２】

【００４３】
表１の如く、各参考例に示すタイヤにおいても、乗り心地性を過度に減じることなく、高速耐久性を向上しうるのが確認できる。
【００４４】
【発明の効果】
叙上の如く本発明は、ベルトプライの外側領域に配されるトッピングゴムの複素弾性率Ｅ＊ｓを中央領域に配されるトッピングゴムの複素弾性率Ｅ＊ｃの１．８〜２．４倍に高めているため、コスト及び重量の上昇を招くことなく高速耐久性を向上できる。
【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】 ベルトプライを説明する断面図である（但し、半径方向内側ゴム（１２ｓｉ）と外側ゴム（１２ｓｏ）との二層構造である、タイヤ軸方向外側の外側領域Ｙｓに配されるトッピングゴム１２ｓを二層に区分することなく図示している）。
【図３】 （Ａ）、（Ｂ）外側領域の区分状態を説明する断面図（但し、半径方向内側ゴム（１２ｓｉ）と外側ゴム（１２ｓｏ）との二層構造である、タイヤ軸方向外側の外側領域Ｙｓに配されるトッピングゴム１２ｓを二層に区分することなく図示している）。
【図４】 本発明のベルトプライの１実施例を示す断面図である。
【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
５ ビードコア
６ カーカス
７ ベルト層
９、９Ａ、９Ｂ ベルトプライ
１０ ベルトコード
１１ コード配列体
１２、１２ｃ、１２ｓ トッピングゴム
Ｓ ベルトプライの側縁
Ｙｓ 外側領域
Ｙｃ 中央領域[0001]
BACKGROUND OF THE INVENTION
In the present invention, the complex elastic modulus of the topping rubber of the belt ply is made different between the outer region and the central region in the tire axial direction, and the belt rigidity in the outer region is relatively increased, so that durability is suppressed while suppressing an increase in weight. It relates to an improved pneumatic tire.
[0002]
[Background Art and Problems to be Solved by the Invention]
The belt layer disposed on the pneumatic tire generally includes a plurality of belt plies in which steel belt cords are arranged at an angle of, for example, 10 to 40 degrees with respect to the tire circumferential direction. It is formed by overlapping.
[0003]
However, at both ends of the belt ply, the belt cord is cut and interrupted, so that the restraining force on the tire is weak, and the shoulder portion is easily refit when traveling at high speed. As a result, the amount of deformation in the shoulder portion increases and the internal temperature increases as the ground pressure increases, so that peeling damage starting from the outer end of the belt tends to occur, and high-speed durability tends to be impaired.
[0004]
Therefore, in the past, in order to enhance this high-speed durability, a band layer in which a band cord such as nylon is spirally wound in the circumferential direction is formed on the outer side in the radial direction of the belt layer to supplement the binding force at the outer end of the belt. In this way, the lifting is suppressed.
[0005]
However, the formation of such a band layer is disadvantageous in that it increases the tire cost and weight.
[0006]
Therefore, the present inventor conducted research by paying attention to the topping rubber constituting the belt ply. As a result, the complex elastic modulus of this topping rubber is made different between the outer region and the central region in the tire axial direction, and the belt rigidity in the outer region is relatively increased, so that deformation in the shoulder portion can be suppressed, such as a band layer It has been found that high-speed durability can be improved without using other members and without impairing riding comfort.
[0007]
That is, according to the present invention, the complex elastic modulus E * s of the topping rubber disposed in the outer region of the belt ply is set to 1.8 to 2.4 times the complex elastic modulus E * c of the topping rubber disposed in the central region. Based on this, an object of the present invention is to provide a pneumatic tire capable of improving high-speed durability without causing an increase in cost and weight and without impairing riding comfort.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the invention of claim 1 of the present application is arranged on the carcass extending from the tread portion through the sidewall portion to the bead core of the bead portion, on the inner side of the tread portion and on the radially outer side of the carcass. A pneumatic tire comprising a belt layer made of a belt ply,
The belt ply has a complex elastic modulus E of a topping rubber formed by covering both surfaces of a cord array in which metal belt cords are aligned with topping rubber and disposed in an outer region including a side edge of the belt ply. * S is characterized by 1.8 to 2.4 times the complex elastic modulus E * c of the topping rubber disposed in the central region between the outer regions.
[0009]
In the invention of claim 1, the region width in the tire axial direction of each outer region on both sides where the central region is disposed between the outer regions is set to 10 to 25% of the ply width of the belt ply,
In the belt ply, the topping rubber in the outer region Ys has a two-layer structure of a radially inner rubber (12si) and an outer rubber (12so), and the complex elastic moduli E * si and E * so of the rubbers are different from each other. ,
Moreover, the complex elastic modulus E * s is the average value of the complex elastic moduli E * si and E * so determined by the following equations when the rubber thicknesses of the rubbers (12si) and (12so) are ti and to , respectively. It is characterized by doing.
(Ti × E * si + to × E * so) / (ti + to)
[0010]
In the invention of claim 2, the topping rubber disposed in the outer region is characterized by comprising a rubber composition containing a resorcin or a resorcin condensate and a methylene donor in a rubber base material.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 illustrates a cross-sectional view when the pneumatic tire 1 of the present invention is a radial tire for a passenger car.
[0012]
In FIG. 1, a pneumatic tire 1 includes a carcass 6 that extends from a tread portion 2 through a sidewall portion 3 to a bead core 5 of a bead portion 4, and a belt layer disposed inside the tread portion 2 and outside the carcass 6. 7 and.
[0013]
The carcass 6 is composed of one or more radial structures in which carcass cords are arranged at an angle of, for example, 75 ° to 90 ° with respect to the tire circumferential direction, in this example, one carcass ply 6A. As the carcass cord, for example, an organic fiber cord such as nylon, polyester, rayon, aromatic polyamide or the like can be suitably used, but a metal cord such as steel can also be adopted as required.
[0014]
The carcass ply 6A has a series of folded portions 6b that are folded back from the inside to the outside around the bead core 5 at both ends of the ply body portion 6a straddling the bead cores 5 and 5. A bead apex rubber 8 for bead reinforcement extending in a tapered shape from the bead core 5 to the outer side in the tire radial direction is disposed between the portion 6b.
[0015]
Next, as shown in FIG. 2, the belt layer 7 has a cord arrangement in which metal belt cords (steel cords in this example) 10 are aligned at an angle of, for example, 15 to 40 ° with respect to the tire circumferential direction. The body 11 is formed from a plurality of belt plies 9A and 9B (in some cases, collectively referred to as belt ply 9) in which both surfaces of the body 11 are covered with a topping rubber 12. The belt ply 9 is placed with different inclination directions so that the belt cord 10 intersects between the plies (note that FIG. 2 shows a radial inner rubber (12si) and an outer rubber (12so). The topping rubber 12s which is a two-layer structure and is disposed in the outer region Ys on the outer side in the tire axial direction is illustrated without being divided into two layers) .
[0016]
In this embodiment, each belt ply 9 has the complex elastic modulus E * s of the topping rubber 12s disposed in the outer region Ys including the side edge thereof disposed in the central region Yc between the outer regions Ys and Ys. The topping rubber 12c is increased to a range of 1.8 to 2.4 times the complex elastic modulus E * c.
[0017]
By changing the rubber complex elastic modulus in this way, the belt rigidity and elasticity are relatively increased and the restraining force is compensated in the outer region Ys, so that the restriction during high-speed running is suppressed. Therefore, the temperature rise at the shoulder portion and the stress acting on the belt outer end can be suppressed low, and peeling damage starting from the belt outer end can be suppressed.
[0018]
In addition, since the belt rigidity in the central region Yc can be kept low, this does not impair riding comfort, and there is no use of other members, which is advantageous for cost reduction and tire weight reduction.
[0019]
Here, the region width Ws in the tire axial direction of the outer region Ys is 10 to 25% of the ply width W0 of the belt ply 9, and this region width Ws is set for each belt ply. That is, as shown in FIGS. 3 (A) and 3 (B) (the belt cord is omitted for convenience. ) Like FIG. 2, it has a two-layer structure of a radially inner rubber (12si) and an outer rubber (12so). In the belt ply 9A on the radially inner side, the top width rubber 12s disposed in the outer region Ys on the outer side in the tire axial direction is illustrated in FIG. In the belt ply 9B on the radially outer side, the area width WsB of the outer area Ys is 10 to 25% of the ply width W0B. At this time, the region width WsA and the region width WsB may be different or equal, but from the viewpoint of suppressing peeling damage, the region width WcA and the region width WcB are set equal in each central region Yc. Is preferred.
[0020]
When the complex elastic modulus E * s of the topping rubber 12s is less than 1.8 times the complex elastic modulus E * c of the topping rubber 12c, the effect of suppressing peeling damage, that is, the effect of improving high-speed durability is not sufficiently exhibited. On the contrary, if it exceeds 2.4 times, although the improvement effect of high-speed durability will increase, riding comfort will fall.
[0021]
Similarly, when the area width Ws is less than 10% of the ply width W0, the effect of improving the high speed durability is not sufficiently exhibited. Conversely, when the area width Ws exceeds 25%, the riding comfort is lowered.
[0022]
The complex elastic modulus is a value measured by using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho Co., Ltd. at a temperature of 70 ° C., a frequency of 10 Hz, an initial strain of 10%, and a dynamic strain of ± 1%.
[0023]
Next, as a means for increasing the complex elastic modulus E * s of the topping rubber 12s, in this example, a resorcin or resorcin condensate and its methylene donor are contained in the rubber base material.
[0024]
Other means for increasing the complex elastic modulus include, for example, increasing the amount of carbon black, increasing the amount of sulfur or vulcanization accelerator as a vulcanizing agent, and increasing the network density of rubber molecules. However, in such a case, there are concerns about a decrease in breaking strength, a decrease in exothermic property, a decrease in workability associated with an increase in the viscosity of the unvulcanized rubber, and therefore use of the resorcinol is preferred.
[0025]
As the rubber substrate, diene rubbers such as natural rubber, butadiene rubber, styrene / butadiene rubber, isoprene rubber, chloroprene rubber, acrylonitrile butadiene rubber can be preferably used, and these can be used alone or in combination. Natural rubber is preferably used from the viewpoint of rubber strength and durability.
[0026]
The resorcin and resorcin condensate are known as phenolic compounds, and undergo a polymerization reaction with the methylene donor during vulcanization to make the topping rubber 12s highly elastic.
[0027]
Examples of the resorcin condensate include condensates of resorcin and aldehydes (so-called resorcin resins), and commercially available resorcin resins include, for example, Penacolite (trademark) resin B-18-S, B- manufactured by Indospec. 20. Sumicanol (trademark) 620 manufactured by Sumitomo Chemical Co., Ltd., R-6 manufactured by Uniroyal, SRF1501 manufactured by Schenectady Chemical, Arofine (trademark) 7209 manufactured by Ashland Chemical, and the like. Resorcinol includes resorcinol manufactured by Sumitomo Chemical Co., Ltd.
[0028]
Examples of the methylene donor include hexamethylenetetramine, hexamethoxymethylolmelamine and derivatives thereof, azadioxabicyclooctane, paraformaldehyde, and the like, and commercially available products include, for example, Coheedur (trademark) A, American Siana manufactured by Bayer. Examples include Midget's Silets (trademark) 966 and 964, Sumitomo Chemical Co., Ltd. Sumikanol (trademark) 507, Uniroyal Corporation M-3, and the like.
[0029]
Here, the content of the resorcin or the resorcin condensate is preferably in the range of 1.0 to 5.0 parts by weight with respect to 100 parts by weight of the rubber base material, and the content of the methylene donor is the resorcin or resorcin. The content of the condensate is preferably 0.5 to 2.0 times.
[0030]
If the content of the resorcin or the resorcin condensate is less than 1.0 part by weight, the elasticity of the topping rubber 12s cannot be sufficiently increased. Conversely, if the content exceeds 5.0 parts by weight, the workability of kneading is increased. The original performance of the topping rubber 12s cannot be ensured, for example, it deteriorates or the adhesiveness decreases. Therefore, the range of 2.0 to 4.0 parts by weight is more desirable.
[0031]
Further, when the content of the methylene donor is less than 0.5 times the content of resorcin, etc., excess unreacted resorcin and the like remain excessively in the rubber, which inhibits adhesion between the rubber and the belt cord. On the other hand, if the ratio exceeds 2.0, excessive methylene donors that do not react reversely remain in the rubber, and similarly, the adhesion between the rubber and the belt cord is inhibited.
[0032]
In the topping rubber 12s, carbon black can be blended as a filler (reinforcing agent), and at this time, it is preferably blended in an amount of 30 to 60 parts by weight with respect to 100 parts by weight of the rubber base material. If the amount of carbon black is less than 30 parts by weight, it will be difficult to achieve high elasticity even when a suitable amount of resorcin, etc. and methylene donor are blended. It causes a marked deterioration of sex.
[0033]
As a filler, in addition to carbon black, other inorganic fillers such as silica and aluminum hydroxide can be blended. Even in such a case, the total blending amount with carbon black is in the range of 30 to 60 parts by weight. It is preferable to do this. Further, conventional additives such as vulcanizing agents, vulcanization accelerators, oils, waxes and the like can be appropriately mixed.
[0034]
As the topping rubber 12c in the central region Yc, a conventional topping rubber that does not contain the resorcinol and its methylene donor in the rubber base material can be employed.
[0035]
In the present invention, as the belt ply 9, as shown in FIG. 4, the topping rubber 12s in the outer region Ys has a two-layer structure of a radially inner rubber 12si and an outer rubber 12so, and each of the rubbers 12si, 12so The complex elastic moduli E * si and E * so are made different from each other. In such a case, when the rubber thicknesses of the rubbers 12si and 12so are set to ti and to , the complex elastic modulus E * s is defined as an average value of the complex elastic modulus E * si and E * so obtained by the following equation.
(Ti × E * si + to × E * so) / (ti + to)
[0036]
Accordingly, if the average value of the complex elastic modulus E * si, E * so (complex elastic modulus E * s) is in the range of 1.8 to 2.4 times the complex elastic modulus E * c, the rubber 12si , 12so can be formed of the same rubber composition as the topping rubber 12c.
[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】
Tires having a tire size of 175 / 70R14 having the structure shown in FIG. 1 were prototyped according to the specifications shown in Table 1, and the ride comfort and high-speed durability of each sample tire were tested. The results are shown in Table 1. The tires have the same specifications except for the belt layer. The specifications of the topping rubber used for the belt ply of the sample tire are shown in Table 2.
[0039]
(1) Ride comfort:
A sample tire is mounted on all wheels of a passenger car (2000cc; FF car) with a rim (14x5JJ) and internal pressure (200Kpa), and runs on a dry asphalt road on a tire test course. Evaluation was performed by a 10-point method (Comparative Example 1 was set to 5 points). The larger the value, the better the ride comfort.
[0040]
(2) High speed durability:
Using a drum tester, the test tire was run for 80 hours at a speed of 150 km / h under a rim (14 × 5JJ), internal pressure (200 Kpa), and load (6.0 kN), and the tire after running was disassembled. The presence or absence of peeling damage at the outer edge of the belt was confirmed.
[0041]
[Table 1]

[0042]
[Table 2]

[0043]
As shown in Table 1, it can be confirmed that the tires shown in the respective reference examples can improve the high-speed durability without excessively reducing the ride comfort.
[0044]
【The invention's effect】
As described above, in the present invention, the complex elastic modulus E * s of the topping rubber disposed in the outer region of the belt ply is 1.8 to 2.4 of the complex elastic modulus E * c of the topping rubber disposed in the central region. Since it is doubled, high-speed durability can be improved without causing an increase in cost and weight.
[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 a cross-sectional view illustrating a belt ply (however, a topping disposed in an outer region Ys on the outer side in the tire axial direction having a two-layer structure of a radially inner rubber (12si) and an outer rubber (12so); The rubber 12s is shown without being divided into two layers) .
FIGS. 3A and 3B are cross-sectional views for explaining a state of division of an outer region (however, a two-layer structure of a radially inner rubber (12si) and an outer rubber (12so); The topping rubber 12s disposed in the outer region Ys is illustrated without being divided into two layers) .
FIG. 4 is a sectional view showing an embodiment of the belt ply of the present invention .
[Explanation of symbols]
2 Tread portion 3 Side wall portion 4 Bead portion 5 Bead core 6 Carcass 7 Belt layers 9, 9A, 9B Belt ply 10 Belt cord 11 Cord array bodies 12, 12c, 12s Topping rubber S Side edge Ys of belt ply Outer region Yc Central region

Claims (2)

A pneumatic tire comprising a carcass extending from a tread portion through a sidewall portion to a bead core of a bead portion, and a belt layer made of a belt ply arranged inward of the tread portion and radially outward of the carcass. ,
The belt ply has a complex elastic modulus E of a topping rubber formed by covering both surfaces of a cord array in which metal belt cords are aligned with topping rubber and disposed in an outer region including a side edge of the belt ply. * S is 1.8 to 2.4 times the complex elastic modulus E * c of the topping rubber disposed in the central region between the outer regions,
The region width in the tire axial direction of each outer region on both sides where the central region is disposed between the outer regions is 10 to 25% of the ply width of the belt ply,
In the belt ply, the topping rubber in the outer region Ys has a two-layer structure of a radially inner rubber (12si) and an outer rubber (12so), and the complex elastic moduli E * si and E * so of the rubbers are different from each other. ,
Moreover, the complex elastic modulus E * s is the average value of the complex elastic moduli E * si and E * so determined by the following equations when the rubber thicknesses of the rubbers (12si) and (12so) are ti and to , respectively. A pneumatic tire characterized by
(Ti × E * si + to × E * so) / (ti + to)   The pneumatic tire according to claim 1, wherein the topping rubber disposed in the outer region is made of a rubber composition containing resorcin or a resorcin condensate and a methylene donor in a rubber base material.

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