JP3774548B2 - Pneumatic radial tire and manufacturing method thereof - Google Patents

Description

表１から明らかなように、本発明タイヤ１，２は従来タイヤ１に比べてカーカスコードの配列状態が良好であると共に、従来タイヤ２，３に比べて発熱性が良好であった。
【００２５】
一方、従来タイヤ１のようにベルト端からショルダー部にかけてカーカスコードに角度θを生じていると、タイヤ充填内圧によってベルト端に剪断歪みを生じ、しかも走行時にカーカスコードが外周成長しようとするので、ベルト層の耐久性を低下させる原因となる。また、従来タイヤ２，３では、部材の追加によってトレッド部における発熱量が増大していた。
【００２６】
【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カーカスコードをタイヤ径方向に配列したカーカス層を装架すると共に、トレッド部におけるカーカス層の外側にスチールコードからなる少なくとも２層のベルト層を層間でコードが互いに交差するように配置し、かつカーカス層に隣接するベルト層のタイヤ周方向に対するコード角度を４５°以下にした空気入りラジアルタイヤを製造するに当たって、カーカス層に隣接するベルト層の幅に対して３５〜７０％の中央領域でカーカスコードを予め波状に型付けしたカーカス材を用いて未加硫のグリーンタイヤを成形し、該グリーンタイヤを加硫成形するようにしたことにより、トレッド部における発熱を増大させることなく、加硫成形時のリフト張力によってショルダー部付近でカーカスコードにウェーブが発生することを防止し、ベルト層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空気入りラジアルタイヤを例示する子午線断面図である。
【図２】図１のタイヤにおけるカーカス層とベルト層を示す平面視展開図である。
【図３】加硫前のカーカスコードを示す平面図である。
【図４】Ｘ線画像による試験タイヤのカーカス層とベルト層を示す部分拡大平面図である。
【符号の説明】
１ ビード部
２ カーカスコード
３ カーカス層
４ ビードコア
６ トレッド部
７ａ〜７ｄ ベルト層
３０ カーカス材[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic radial tire suitable for heavy loads used for trucks, buses, and the like, and a method for manufacturing the same, and more specifically, without increasing heat generation in a tread portion, and by a lift tension at the time of vulcanization molding. The present invention relates to a pneumatic radial tire and a method for manufacturing the same, which prevent a wave from being generated in a carcass cord near a portion.
[0002]
[Prior art]
Conventional pneumatic radial tires are generally arranged between a tread and a carcass layer so that at least two belt layers inclined with respect to the circumferential direction of the steel cord intersect each other while the carcass layer carcass layer has a carcass layer carcass layer. The cord is arranged at approximately 90 ° with respect to the tire circumferential direction. When manufacturing a pneumatic radial tire configured in this way, insert an unvulcanized green tire into the mold, apply lift tension from the inside and press it against the inner surface of the mold to obtain the shape of the product tire Molding.
[0003]
However, when the cord angle of the belt layer adjacent to the carcass layer with respect to the tire circumferential direction is small, the cord angle of the belt layer changes due to the lift tension at the time of vulcanization molding, and the shoulder portion is dragged by the angle change of the belt layer. There was a problem that a wave was generated in the carcass chord in the vicinity. When a wave is generated in the carcass cord in the vicinity of the shoulder portion in this way, a force is applied to make the carcass cord straight due to the tire filling internal pressure, so that shear distortion occurs in the belt end region, and the excess length of the carcass cord periphery Since the outer periphery is to be grown during running, the durability of the belt layer is lowered.
[0004]
Therefore, as a countermeasure against the above problem, it is conceivable to add a high-angle belt to the outside of the carcass layer so that the angle change of the belt layer is not transmitted to the carcass cord. However, for heavy-duty pneumatic radial tires used for running on rough land, it is necessary to ensure cut resistance and envelope characteristics, so it is inappropriate to use the above high-angle belt. Since the tread thickness increases, the amount of heat generated in the tread portion increases.
[0005]
Further, by interposing a cushion rubber between the carcass layer and the belt layer, it is possible to prevent the change in the angle of the belt layer from being transmitted to the carcass cord. However, also in this case, since the tread thickness is increased by the cushion rubber, the amount of heat generated in the tread portion is increased.
[0006]
[Problems to be solved by the invention]
An object of the present invention is to provide a pneumatic radial tire and a method for manufacturing the same that can prevent a carcass cord from generating waves near the shoulder portion due to lift tension during vulcanization molding without increasing heat generation in the tread portion. It is to provide.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, a pneumatic radial tire according to the present invention includes a carcass layer in which carcass cords are arranged in a tire radial direction between a pair of left and right bead portions and a steel on the outside of the carcass layer in a tread portion. In a pneumatic radial tire in which at least two belt layers made of cords are arranged so that the cords cross each other between the layers, and a cord angle with respect to a tire circumferential direction of a belt layer adjacent to the carcass layer is 45 ° or less, The carcass cord is wave-shaped in a central region of 35 to 70% with respect to the width of the belt layer adjacent to the carcass layer.
[0008]
In the pneumatic radial tire manufacturing method of the present invention, a carcass layer in which carcass cords are arranged in the tire radial direction is mounted between a pair of left and right bead portions, and a steel cord is provided outside the carcass layer in the tread portion. A pneumatic radial tire manufacturing method in which at least two belt layers are arranged such that the cords intersect each other between the layers, and the cord angle of the belt layer adjacent to the carcass layer with respect to the tire circumferential direction is 45 ° or less. Then, an unvulcanized green tire is formed using a carcass material in which a carcass cord is pre-corrugated in a central region of 35 to 70% with respect to the width of the belt layer adjacent to the carcass layer. It is characterized in that it is subjected to sulfur molding.
[0009]
Thus, when manufacturing a pneumatic radial tire in which the cord angle of the belt layer adjacent to the carcass layer is 45 ° or less with respect to the tire circumferential direction, the center of 35 to 70% with respect to the width of the belt layer adjacent to the carcass layer By forming an unvulcanized green tire using a carcass material in which carcass cords are pre-corrugated in the region, the green tire is vulcanized and molded, so that the belt layer is formed by the lift tension at the time of vulcanization molding. Even when the cord angle changes, the carcass cord wavy portion in the central region absorbs the distortion caused by the angle change of the belt layer, so that it is possible to prevent the carcass cord from generating waves near the shoulder portion. Moreover, according to the said structure, since it is not necessary to add a tire member newly, the emitted-heat amount in a tread part is not increased.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.
1 to 3 illustrate a heavy duty pneumatic radial tire according to an embodiment of the present invention. In the figure, a carcass layer 3 in which a plurality of carcass cords 2 are arranged in the tire radial direction is mounted between a pair of left and right bead portions 1, 1, and both ends of the carcass layer 3 in the tire width direction are bead cores. 4 is wound around the tire from the inside to the outside. The bead portion 1 is provided with a reinforcing layer 5 so as to wrap the carcass layer 3.
[0011]
Four belt layers 7 a to 7 d each made of a plurality of steel cords are provided outside the carcass layer 3 in the tread portion 6. The belt layers 7a to 7d are arranged such that the cords are inclined with respect to the tire circumferential direction and the cords cross each other between the layers. On the other hand, the carcass cord 2 is wave-shaped in a central region C of 35 to 70% with respect to the belt width W of the belt layer 7a adjacent to the carcass layer 3, and the outer side of the central region C is in the tire circumferential direction. They are arranged so that the angle is substantially 90 °.
[0012]
The first belt layer 7a counted from the carcass layer side has a cord angle with respect to the tire circumferential direction set to 22 to 45 °. The cord angle of the second belt layer 7b with respect to the tire circumferential direction is set to 18 to 27 °. The cord angle with respect to the tire circumferential direction of the third belt layer 7c is set to 14 to 24 °. In the fourth belt layer 7d, the cord angle with respect to the tire circumferential direction is set to 18 to 27 °. The cord angles of these belt layers 7a to 7d are set in a range suitable for heavy loads.
[0013]
In the present invention, in manufacturing the pneumatic radial tire, the carcass material in which the carcass cord 2 is wave-shaped in advance in the center region C of 35 to 70% with respect to the belt width W of the belt layer 7a adjacent to the carcass layer 3 is produced. 30 is used to form an unvulcanized green tire. Then, the unvulcanized green tire is inserted into a mold, and a groove 8 or the like is formed in the tread portion 6 by applying lift tension from the inside through a bladder or the like and pressing it against the inner surface of the mold. Vulcanize.
[0014]
In this way, by carving the carcass cord 2 in the center region C in advance, even if the cord angle of the belt layer 7a changes due to the lift tension at the time of vulcanization molding, the distortion due to the angle change of the belt layer 7a is centered. Since the wavy portion of the carcass cord 2 in the region C is absorbed, it is possible to prevent the wave from being generated in the carcass cord 2 near the shoulder portion.
[0015]
In addition, since the carcass tension is hardly applied in the central region C, the carcass cord 2 does not grow on the outer periphery during running even if the carcass cord 2 is wave-shaped. Therefore, the durability of the belt layers 7a to 7d provided outside the carcass layer 3 can be improved. Moreover, according to the said structure, since it is not necessary to add cushion rubber | gum and a high angle belt unlike the past, the thickness of the tread part 6 can be made thin compared with the past, and the emitted-heat amount in the tread part 6 can be made low. In addition, the material cost can be reduced by the amount of the additional member.
[0016]
In the present invention, the central region C where the carcass cord 2 is wave-shaped is set to a range of 35 to 70% with respect to the belt width W of the belt layer 7 a adjacent to the carcass layer 3. That is, the change in the angle of the belt layer 7a due to the lift tension is not uniform in the tire width direction, and is particularly large near the center in the tire width direction, so the central region C covers at least 35% of the belt width W of the belt layer 7a. There is a need. On the other hand, if the center region C exceeds 70% of the belt width W of the belt layer 7a, the excess length peripheral of the wavy portion remaining after the vulcanization molding tends to grow on the outer periphery during running, so that the durability of the belt layer decreases. End up.
[0017]
The amplitude a of the carcass cord 2 in the central region C is preferably 4 to 8 times the carcass cord diameter Φ before vulcanization. If the amplitude a of the carcass cord 2 is less than four times the carcass cord diameter Φ, the distortion due to the angle change of the belt layer 7a cannot be absorbed. Since there are too many, there exists a possibility of outer periphery growth at the time of driving | running | working. The wavelength λ of the carcass cord 2 is preferably 4 to 10 times the amplitude a.
[0018]
The amplitude a and wavelength λ of the carcass cord 2 are set in advance in the carcass material 30 before vulcanization. In general, the cord tension applied to the carcass cord 2 of the unvulcanized tire from the molding process of the primary green tire by the molding drum to the vulcanization molding process through the belt bonding process is the same as that of the carcass cord 2 previously shaped in a wave shape. The amplitude a is not greatly reduced. Therefore, the amplitude “a” in the vulcanized tire is 2 to 7 times the carcass cord diameter Φ in the central region of the crown portion, and 1 to 5 times the carcass cord diameter Φ in the outer edge portion of the wavy portion.
[0019]
The present invention is preferably applied to a wasteland running tire having a groove 8 having a groove depth of 35 mm or more in the tread portion 6. When such a wasteland running tire is vulcanized using a split mold, the belt lift rate at the time of vulcanization molding is high, so that a remarkable effect can be obtained by applying the present invention.
In the above-described embodiment, the belt layer has been described as having four layers, but at least two layers may be provided. As the carcass cord, a polyester cord, a rayon cord, a nylon cord, an aromatic polyamide fiber cord, etc. can be used in addition to a steel cord.
[0020]
【Example】
The tire size of 23.5R25, the radial tire structure shown in FIG. 1, and the carcass cords of the present invention 1 and 2 having different amplitudes a and wavelengths λ before vulcanization, and the carcass cords are wave-shaped. The cord angle with respect to the tire circumferential direction is 48 ° between the conventional tire 1 that is not used, the conventional tire 2 in which a cushion rubber having a thickness of 5 mm is interposed between the belt layer and the carcass layer, and the belt layer and the carcass layer. A conventional tire 3 with a high-angle belt inserted was produced. In each tire, the configuration of the belt layer and the carcass layer was as follows.
[0021]
Belt layer 1st: Steel cord (3 + 9 + 15 × 0.22), angle 32 °
2nd: Steel cord (3 + 9 + 15 × 0.22), angle 24 °
Third: Steel cord (3 x 7 x 0.24 HE), angle 22 °
4th: Steel cord (3 x 7 x 0.24 HE), angle 22 °
Carcass layer steel cord (7 × 7 × 0.23)
Carcass cord diameter Φ = 2.08mm
For these test tires, the arrangement of the carcass cords after vulcanization was evaluated by the following test method, and the heat generation was evaluated. The results are shown in Table 1.
[0022]
Carcass cord arrangement after vulcanization:
Each test tire after vulcanization was X-rayed at four locations in the tire circumferential direction, and the angle θ of the carcass cord with respect to the radial direction at the belt edge was measured as shown in FIG. The evaluation results are indicated by evaluation points CW0 to CW5 classified as follows. CW0 to CW2 are good tires, but CW3 to CW5 are bad tires.
[0023]
CW0: 0 ° ≦ θ <4 °
CW 1 : 4 ° ≦ θ <8 °
CW 2 : 8 ° ≦ θ <12 °
CW 3 : 12 ° ≦ θ <15 °
CW 4 : 15 ° ≦ θ <18 °
CW 5 : 18 ° ≦ θ
Exothermic:
Each test tire was run on the test drum under conditions of an air pressure of 500 kPa and a speed of 10 km / h, and after running for 12 hours, the internal temperature of the tread in the fourth belt layer in the center portion in the tread width direction was measured. The evaluation results are shown as an index with the reciprocal of the measured value of the conventional tire 2 being 100. The larger the index value, the smaller the calorific value.
[0024]

As is clear from Table 1, the tires 1 and 2 of the present invention have a better carcass cord arrangement than the conventional tire 1 and better heat generation than the conventional tires 2 and 3.
[0025]
On the other hand, when the angle θ is generated in the carcass cord from the belt end to the shoulder portion as in the conventional tire 1, shear distortion occurs in the belt end due to the tire filling internal pressure, and the carcass cord tends to grow on the outer periphery during running. This causes a decrease in the durability of the belt layer. Further, in the conventional tires 2 and 3, the amount of heat generated in the tread portion has increased due to the addition of members.
[0026]
【The invention's effect】
As described above, according to the present invention, a carcass layer in which carcass cords are arranged in the tire radial direction is mounted between a pair of left and right bead portions, and at least two layers of steel cords are formed outside the carcass layer in the tread portion. Of the belt layer adjacent to the carcass layer, and the belt layer adjacent to the carcass layer is disposed at a cord angle of 45 ° or less with respect to the tire circumferential direction. An unvulcanized green tire is molded using a carcass material in which a carcass cord is pre-corrugated in a central region of 35 to 70% with respect to the width of the belt layer to be formed, and the green tire is vulcanized and molded. By increasing the lift tension during vulcanization without increasing heat generation in the tread Prevents wave is generated in the carcass cords, it is possible to improve the durability of the belt layer.
[Brief description of the drawings]
FIG. 1 is a meridian cross-sectional view illustrating a pneumatic radial tire according to an embodiment of the invention.
2 is a development plan view showing a carcass layer and a belt layer in the tire of FIG. 1. FIG.
FIG. 3 is a plan view showing a carcass cord before vulcanization.
FIG. 4 is a partially enlarged plan view showing a carcass layer and a belt layer of a test tire based on an X-ray image.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Bead part 2 Carcass cord 3 Carcass layer 4 Bead core 6 Tread part 7a-7d Belt layer 30 Carcass material

Claims (3)

A carcass layer in which carcass cords are arranged in the tire radial direction is mounted between a pair of left and right bead portions, and at least two belt layers made of steel cords outside the carcass layer in the tread portion, the cords cross each other between the layers. And a pneumatic radial tire in which the cord angle of the belt layer adjacent to the carcass layer with respect to the tire circumferential direction is 45 ° or less, 35 to 70 with respect to the width of the belt layer adjacent to the carcass layer. A pneumatic radial tire in which the carcass cord is wave-shaped in the center region of%. A carcass layer in which carcass cords are arranged in the tire radial direction is mounted between a pair of left and right bead portions, and at least two belt layers made of steel cords outside the carcass layer in the tread portion, the cords cross each other between the layers. In the pneumatic radial tire manufacturing method in which the cord angle of the belt layer adjacent to the carcass layer with respect to the tire circumferential direction is 45 ° or less, with respect to the width of the belt layer adjacent to the carcass layer A pneumatic radial tire manufacturing method in which an unvulcanized green tire is molded using a carcass material in which a carcass cord is pre-corrugated in a central region of 35 to 70%, and the green tire is vulcanized. The method for manufacturing a pneumatic radial tire according to claim 2, wherein the amplitude of the carcass cord in the central region is 4 to 8 times the carcass cord diameter before vulcanization, and the wavelength is 4 to 10 times the amplitude.

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