JP4259732B2 - Pneumatic tire and manufacturing method thereof - Google Patents

Description

【００３２】
この表１から判るように、本発明タイヤは従来タイヤに比べてランフラット耐久性が優れていた。
【００３３】
【発明の効果】
以上説明したように本発明によれば、左右一対のビード部間に複数層のカーカス層を装架し、少なくともカーカス層の層間にサイドウォール部に沿って延在する断面三日月状のゴム補強層を設けた空気入りタイヤにおいて、カーカス層のカーカスコードをタイヤ径方向に対して傾斜させ、これらカーカス層のタイヤ径方向に対するコード角度の絶対値を最内層から最外層に向けて徐々に大きくしたから、パンク走行時の耐久性を向上し、優れたランフラット性を発揮することが可能になる。
【図面の簡単な説明】
【図１】本発明の実施形態からなる空気入りタイヤを示す半断面図である。
【図２】図１の空気入りタイヤにおけるカーカス層のコード角度を示す説明図である。
【符号の説明】
１ ビード部
２ トレッド部
３ サイドウォール部
４ ビードコア
５Ａ〜５Ｃ ゴム補強層
６ インナーライナー層
７ ベルト層
Ｐ１〜Ｐ３ カーカス層
Ｒ タイヤ径方向
α コード角度[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic tire having run-flat properties and a method for manufacturing the same, and more particularly to a pneumatic tire configured to improve durability during puncture traveling and a method for manufacturing the same.
[0002]
[Prior art]
In recent years, a pneumatic tire having run-flatness has been proposed in which a rubber reinforcing layer having a crescent cross section is embedded in a sidewall portion. In this pneumatic tire, a plurality of carcass layers are mounted between a pair of left and right bead portions, and a crescent-shaped rubber reinforcement layer extending along the sidewall portions on the inner surface of the innermost layer or between the carcass layers. It has a configuration provided.
[0003]
The pneumatic tire having the run-flat property configured as described above suppresses the bending of the sidewall portion based on the rigidity of the rubber reinforcing layer having a crescent-shaped cross section. It is possible to travel a certain distance.
[0004]
However, when a rubber reinforcing layer having a crescent-shaped cross section is inserted between the layers of the carcass layer, the degree of pulling of the carcass layer generated when the green tire is vulcanized is greatly different for each carcass layer. That is, the degree to which the left and right bead portions pull the carcass layer is caused by the difference between the green tire periphery and the vulcanized periphery. Depending on the existence, the carcass layer will vary greatly. If the carcass layer pulling degree differs greatly for each carcass layer in this way, the tension of each carcass layer during non-inflation becomes non-uniform, and stress concentration occurs on a specific carcass layer during puncturing, resulting in a run flat. There was a problem that durability as a tire was insufficient.
[0005]
[Problems to be solved by the invention]
An object of the present invention is to provide a pneumatic tire having run flatness with improved durability during puncturing and a method for manufacturing the same.
[0006]
[Means for Solving the Problems]
A pneumatic tire according to the present invention for solving the above-described object is provided with a plurality of carcass layers mounted between a pair of left and right bead portions, and at least a crescent cross section extending along a sidewall portion between the carcass layers. In a pneumatic tire provided with a rubber reinforcing layer, the carcass cord of the carcass layer is inclined with respect to the tire radial direction, and the absolute value of the cord angle of the carcass layer with respect to the tire radial direction is directed from the innermost layer to the outermost layer. It is characterized by gradually increasing.
[0007]
Further, the method for manufacturing a pneumatic tire according to the present invention has a crescent-shaped cross section in which a plurality of carcass layers are mounted between a pair of left and right bead portions, and extend along the sidewall portions at least between the carcass layers. In the method of manufacturing a pneumatic tire provided with a rubber reinforcing layer, the carcass cords of the carcass layer are inclined with respect to the tire radial direction, and the absolute value of the cord angle of the carcass layer with respect to the tire radial direction is changed from the innermost layer to the outermost layer. A green tire that is gradually enlarged is formed, and the green tire is expanded in a mold and vulcanized.
[0008]
Thus, in the pneumatic tire having the run-flat property provided with the rubber reinforcement layer having a crescent cross section in the sidewall portion, the carcass cord of the carcass layer is inclined with respect to the tire radial direction, and the cord of the carcass layer with respect to the tire radial direction is provided. By gradually increasing the absolute value of the angle from the innermost layer to the outermost layer, the tension applied to each carcass layer during vulcanization molding can be absorbed based on the difference in cord angle, resulting in non-inflation. The tension of the carcass layer at the time becomes substantially uniform. Therefore, it is possible to avoid stress concentration on the carcass layer during puncturing and to improve durability as a run-flat tire.
[0009]
In the present invention, in order to sufficiently ensure the run-flat property, it is preferable to provide a crescent-shaped rubber reinforcing layer extending along the sidewall portion not only between the layers of the carcass layer but also on the inner surface of the innermost layer.
[0010]
In order to make the tension of the carcass layer in non-inflation substantially uniform, the relationship in which the absolute value of the cord angle of the carcass layer with respect to the tire radial direction gradually increases from the innermost layer to the outermost layer is However, in order to achieve such a cord angle relationship, the cord angles of the carcass layers adjacent to each other in the state of a green tire (unvulcanized tire) must be maintained. The difference in absolute value is preferably set to 4 ° or more.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.
[0012]
FIG. 1 shows a pneumatic tire according to an embodiment of the present invention. In FIG. 1, 1 is a bead part, 2 is a tread part, 3 is a side wall part which connects the bead part 1 and a tread part mutually. A plurality of carcass layers P1 to P3 are mounted between the pair of left and right bead portions 1 and 1. The carcass layer P1 serving as the innermost layer has both ends in the tire width direction wound around the bead core 4 from the inside to the outside of the tire, and the terminal ends near the tire maximum width position. The carcass layer P <b> 2 that is an intermediate layer has both ends in the tire width direction wound around the bead core 4 from the inside to the outside of the tire, and ends at a position on the outer peripheral side of the bead core 4. The carcass layer P <b> 3 that is the outermost layer is disposed so that both ends in the tire width direction pass outside the bead core 4, and the terminal ends at a position on the inner peripheral side of the bead core 4.
[0013]
Between the outermost carcass layer P3 and the intermediate carcass layer P2, a crescent-shaped rubber reinforcing layer 5A extending along the sidewall portion 3 is inserted. The rubber reinforcing layer 5A corresponds to a bead filler in a normal pneumatic tire, but extends to the tread side so as to exhibit run flatness. Between the intermediate carcass layer P2 and the innermost carcass layer P1, a crescent-shaped rubber reinforcing layer 5B extending along the sidewall portion 3 is inserted. Further, a crescent-shaped rubber reinforcing layer 5C extending along the sidewall portion 3 is also provided on the inner surface of the innermost carcass layer P1.
[0014]
These rubber reinforcing layers 5A to 5C are made of a rubber composition harder than the rubber composition on the outer surface of the sidewall, and gradually become thinner from the vicinity of the tire maximum width position toward the tread side. The hardness of each rubber reinforcement layer 5A-5C is good to set it as the range of 70-90 in JIS-A hardness. Furthermore, the thickness of each rubber reinforcing layer 5A to 5C at the maximum tire width position is preferably in the range of 2.5 to 4.5 mm.
[0015]
An inner liner layer 6 is provided on the inner surface of the tire. On the other hand, on the outer peripheral side of the carcass layers P <b> 1 to P <b> 3 in the tread portion 2, two layers of belt layers 7 and 7 formed by aligning a plurality of reinforcing cords in parallel are provided. These belt layers 7 and 7 are disposed such that the reinforcing cords are inclined with respect to the tire circumferential direction and the reinforcing cords cross each other between the layers. Further, on the outer peripheral side of the belt layers 7, a belt cover layer 8 is provided in which reinforcing cords are oriented in the tire circumferential direction.
[0016]
In the pneumatic tire, as shown in FIG. 2, the carcass cords of the carcass layers P1 to P3 are inclined with respect to the tire radial direction R, and the carcass layers P1 to P3 have a cord angle α with respect to the tire radial direction R. The absolute value is set to gradually increase from the innermost layer to the outermost layer. That is, the cord angle α of the carcass layers P1 to P3 has the relationship of the following expression (1).
[0017]
| Α (P1) | <| α (P2) | <| α (P3) | (1)
However, the formula (1) is a relational expression when the carcass layer is three layers, and when the carcass layer is an N layer (N: any integer of 2 or more), the relation of the following formula (2) is satisfied. Just do it.
[0018]
| Α (P1) | <... <| α (PN) | (2)
In the present invention, the absolute value of the cord angle α needs to have the above relationship, but the inclination direction of the carcass cord is not particularly limited, and the carcass cords of the adjacent carcass layers are inclined in the same direction. You may make it incline in the direction opposite to each other.
[0019]
When the pneumatic tire is manufactured, the carcass cords of the carcass layers P1 to P3 are inclined with respect to the tire radial direction R, and the absolute value of the cord angle α with respect to the tire radial direction R of the carcass layers P1 to P3 is determined from the innermost layer. A green tire that is gradually enlarged toward the outermost layer is molded, and the green tire is set in a mold, and then the mold is formed by inflating the green tire by applying pressure from the inside of the tire using a bladder or the like. It is sufficient to press against the inner surface and perform vulcanization in that state.
[0020]
In the vulcanization molding step, since a rubber reinforcing layer having a crescent cross section is interposed between the carcass layers P1 to P3, the carcass layer P3 located on the outer side is subjected to a larger tensile force as the green tire swells. However, the difference in the pulling force can be leveled based on the change in the cord angle α. That is, the difference between the green tire periphery and the vulcanized periphery can be replaced by the change in the cord angle α of the carcass layers P1 to P3, so that the absolute value of the cord angle α in the state of the green tire is changed to the outer carcass layer. By setting as large as P3, the tension applied to the carcass layers P1 to P3 can be made uniform.
[0021]
The difference in absolute value of the cord angle α between the carcass layers adjacent to each other in the state of the green tire is preferably set to 4 ° or more. By making the cord angle α of the carcass layers P1 to P3 in the above relationship in the state of the green tire, the absolute value of the cord angle α with respect to the tire radial direction R of the carcass layers P1 to P3 is changed from the innermost layer to the outermost layer even after vulcanization. Since the relationship that gradually increases toward the left remains, it is possible to reliably prevent the tension from being biased to any of the carcass layers P1 to P3.
[0022]
The pneumatic tire described above is provided with rubber reinforcing layers 5A to 5C having a crescent-shaped cross section in the sidewall portion 3, and the bending of the sidewall portion 3 is suppressed based on the rigidity of these rubber reinforcing layers 5A to 5C. Even in the state, the vehicle can travel a certain distance at a certain speed. That is, it has run flatness.
[0023]
Further, the carcass layers P1 to P3 are pulled to the tread side by a lift during vulcanization molding of the green tire, but the tension is absorbed based on the change in the cord angle α of the carcass layers P1 to P3. The tension of the carcass layers P1 to P3 at the time becomes substantially uniform. Therefore, it is possible to avoid stress concentration on any of the carcass layers P1 to P3 during puncturing, and to improve the durability as a run-flat tire.
[0024]
As the carcass cord in the present invention, a textile cord or a steel cord can be used. The fineness of the textile cord, the twisted structure, and the number of ends (the number of driven parts per unit width) may be within the range used as a conventionally known carcass cord. Textile cord materials include nylons such as nylon 66 and nylon 64, polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate, rayon, vinylon, acrylic, aramid, poly-p-phenylenebenzbisoxazole, and fat. Group polyketone and the like. On the other hand, the strand diameter, the twisted structure, and the number of ends of the steel cord may be within a range that is used as a conventionally known steel cord for tire reinforcement.
[0025]
The present invention is preferably applied to conventionally known pneumatic radial tires for passenger cars. If the present invention is applied to a pneumatic radial tire for a passenger car, it is possible to improve the reliability during puncturing even when a spare tire is not mounted on the vehicle. In order to exhibit the same tire performance as that of the pneumatic radial tire, in the pneumatic tire after vulcanization, the cord angle α with respect to the tire radial direction R of each carcass layer should be in the range of 0 ° to 10 °. preferable.
[0026]
【Example】
The tire of the present invention in which the cord angle with respect to the tire radial direction of the three carcass layers is set to a predetermined relationship based on the following manufacturing method in a pneumatic tire (FIG. 1) having a run-flat property of tire size 225 / 60R16 Each tire was made.
[0027]
Invention tire:
The carcass cords of all the carcass layers are inclined with respect to the tire radial direction, and the absolute values of the cord angles of these carcass layers with respect to the tire radial direction are gradually increased from the innermost layer to the outermost layer. A green tire in which the difference between the absolute values of the cord angles was set to 4 ° was molded, and the green tire was expanded in a mold and vulcanized. Also in the vulcanized tire, the absolute value of the cord angle α with respect to the tire radial direction of the carcass layer gradually increased from the innermost layer toward the outermost layer.
[0028]
Conventional tire:
Green tires in which the cord angles of all the carcass layers with respect to the tire radial direction were set to approximately 0 ° were molded, and the green tires were expanded in a mold and vulcanized. Also in the tire after vulcanization, the cord angle α with respect to the tire radial direction of all the carcass layers was substantially 0 °.
[0029]
When these test tires were evaluated for run flat durability under the following conditions, the results shown in Table 1 were obtained.
[0030]
Run-flat durability:
After assembling each test tire on a rim with a rim size of 16x71 / 2JJ, with the air removed, it was mounted on the right side of the front wheel of a 4000cc rear-wheel drive vehicle, and an elliptical course was run at a speed of 80km / h. Measured the distance until the test driver felt abnormal vibration due to tire failure and stopped driving. As an evaluation result, the conventional tire is shown as an index of 100. The larger the index value, the better the run flat durability.
[0031]
[Table 1]

[0032]
As can be seen from Table 1, the tire of the present invention was superior in run-flat durability compared to the conventional tire.
[0033]
【The invention's effect】
As described above, according to the present invention, a plurality of carcass layers are mounted between a pair of left and right bead portions, and at least a crescent-shaped rubber reinforcement layer extending along the sidewall portions between the carcass layers. Since the carcass cord of the carcass layer is inclined with respect to the tire radial direction and the absolute value of the cord angle of the carcass layer with respect to the tire radial direction is gradually increased from the innermost layer toward the outermost layer. It is possible to improve durability during puncture driving and to exhibit excellent run flatness.
[Brief description of the drawings]
FIG. 1 is a half sectional view showing a pneumatic tire according to an embodiment of the present invention.
2 is an explanatory diagram showing a cord angle of a carcass layer in the pneumatic tire of FIG. 1. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Bead part 2 Tread part 3 Side wall part 4 Bead core 5A-5C Rubber reinforcement layer 6 Inner liner layer 7 Belt layer P1-P3 Carcass layer R Tire radial direction (alpha) Cord angle

Claims (5)

A pneumatic tire in which a plurality of carcass layers are mounted between a pair of left and right bead portions, and at least a crescent-shaped rubber reinforcing layer extending along a sidewall portion is provided between the carcass layers. A pneumatic tire in which the carcass cords of the layers are inclined with respect to the tire radial direction, and the absolute values of the cord angles of the carcass layers with respect to the tire radial direction are gradually increased from the innermost layer toward the outermost layer. The pneumatic tire according to claim 1, wherein a rubber reinforcing layer having a crescent cross section extending along the sidewall portion is provided on an inner surface of the carcass layer and an inner surface of the innermost layer. In a method for manufacturing a pneumatic tire in which a plurality of carcass layers are mounted between a pair of left and right bead portions, and a crescent-shaped rubber reinforcing layer extending along a sidewall portion is provided at least between the carcass layers. The carcass cord of the carcass layer is inclined with respect to the tire radial direction, and a green tire is formed by gradually increasing the absolute value of the cord angle with respect to the tire radial direction of the carcass layer from the innermost layer to the outermost layer, A method for producing a pneumatic tire in which a green tire is vulcanized by expanding in a mold. The method for producing a pneumatic tire according to claim 3, wherein a rubber reinforcing layer having a crescent cross section extending along the sidewall portion is provided on an inner surface of the carcass layer and an inner surface of the innermost layer. The manufacturing method of the pneumatic tire of Claim 3 or Claim 4 which sets the difference of the absolute value of the cord angle of the carcass layer which mutually adjoins in the state of the said green tire to 4 degrees or more.

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