JP4270374B2 - Pneumatic tire and tire mold - Google Patents

Description

【００２６】
この表１から判るように、実施例１〜４では、周方向溝の溝底にオーバーフローによる薄膜が形成された場合であっても、薄膜における亀裂の発生を抑制し、溝底でのクラックの発生を抑制することができた。
【００２７】
【発明の効果】
以上説明したように本発明によれば、トレッド部を成形する部位がタイヤ径方向の分割面を介して複数に分割されているモールドを用いて、トレッド部にタイヤ周方向に延びる周方向溝を備えた空気入りタイヤを製造するに際して、周方向溝がモールドの分割面によって区画される部分の道のりＬ’をその直線距離Ｌよりも長くし、周方向溝が分割面によって区画される部分の道のりＬ’が直線距離Ｌに対して１．１Ｌ≦Ｌ’の関係を満足するようにしたから、周方向溝の溝底にオーバーフローによる薄膜が形成された場合であっても、薄膜における亀裂の発生を抑制し、更には溝底でのクラックの発生を抑制することができる。
【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タイヤのトレッドパターンを示す平面図である。
【図２】本発明の実施形態からなるタイヤ用モールドのトレッド成形部位を示す平面図である。
【図３】図１における周方向溝の要部を拡大して示す平面図である。
【図４】図２における周方向溝成形骨の要部を拡大して示す平面図である。
【図５】分割される部分の形状が種々異なる周方向溝成形骨を示し、（ａ）〜（ｄ）はそれぞれ要部拡大平面図である。
【図６】分割される部分の形状が種々異なる周方向溝成形骨によって得られる溝底の薄膜を示し、（ａ）〜（ｄ）はそれぞれ要部拡大平面図である。
【図７】（ａ）〜（ｃ）は従来の空気入りタイヤにおけるクラック発生のメカニズムを説明するための説明図である。
【符号の説明】
１ トレッド部
２ 主溝
３ 副溝
４ 陸部
５ 薄膜
１１ａ，１１ｂ モールド
１２ 周方向溝成形骨
１３ 副溝成形骨
Ｘ 分割面[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic tire provided with a circumferential groove extending in the tire circumferential direction in a tread portion and a mold for manufacturing the pneumatic tire, and more particularly, when a thin film due to overflow is formed on the groove bottom of the circumferential groove. Even so, the present invention relates to a pneumatic tire and a tire mold in which generation of cracks at the groove bottom caused by the thin film is suppressed.
[0002]
[Prior art]
As a mold (die) for manufacturing a pneumatic tire having a circumferential groove extending in the tire circumferential direction in the tread portion, a portion for molding the tread portion is divided into a plurality through a tire radial direction dividing surface. A sectional type mold is generally used (see, for example, Patent Document 1).
[0003]
However, when manufacturing a pneumatic tire using a sectional type mold as described above, a thin film due to overflow is formed at the groove bottom of the circumferential groove due to minute misalignment of the mold or gaps between the molds caused by repeated use. Sometimes formed. When a thin film due to overflow is formed at the groove bottom of the circumferential groove in this way, the thin film cracks due to the movement of the tread portion when the tire is running, and it reaches the groove bottom, and a crack is generated at the groove bottom. There is a problem.
[0004]
Here, the mechanism of crack generation will be described with reference to FIGS. In FIG. 7A, an overflow thin film 23 is formed at the groove bottom of a circumferential groove 22 that divides the land portion (rib) 21. As shown in FIG. 7B, a crack 24 is formed in the thin film 23 due to the movement of the land portion 21 during tire travel. Then, as shown in FIG. 7C, the crack 24 gradually grows in the depth direction, reaches the groove bottom of the circumferential groove 22, and further expands along the longitudinal direction of the circumferential groove 22. become.
[0005]
Therefore, in a sectional type mold, it has been studied to prevent overflow at the groove bottom of the circumferential groove, but it is extremely difficult to completely prevent the overflow as described above due to the mold mechanism.
[0006]
[Patent Document 1]
Japanese Laid-Open Patent Publication No. 6-218733
[Problems to be solved by the invention]
An object of the present invention is for a pneumatic tire and a tire in which generation of cracks at the groove bottom caused by the thin film is suppressed even when a thin film due to overflow is formed at the groove bottom of the circumferential groove. It is to provide a mold.
[0008]
[Means for Solving the Problems]
The pneumatic tire of the present invention for solving the above-described object includes a circumferential groove extending in a tire circumferential direction in a tread portion, and a portion where the tread portion is molded is divided into a plurality through a tire radial direction dividing surface. In the pneumatic tire manufactured by the molded mold, the path L ′ of the portion where the circumferential groove is defined by the dividing surface is made longer than the linear distance L, and the circumferential groove is defined by the dividing surface. This is characterized in that the road L ′ of the portion to be satisfied satisfies the relationship of 1.1L ≦ L ′ with respect to the straight line distance L.
[0009]
On the other hand, a tire mold of the present invention for solving the above-mentioned object is a mold for manufacturing a pneumatic tire provided with a circumferential groove extending in a tire circumferential direction in a tread portion, and molds the tread portion. In the mold in which the part is divided into a plurality of parts through the dividing surface in the tire radial direction, the circumferential direction groove L ′ of the part defined by the dividing surface is made longer than the linear distance L , and the circumferential direction The path L ′ where the groove is defined by the dividing surface satisfies the relationship 1.1L ≦ L ′ with respect to the linear distance L.
[0010]
However, the road L ′ and the straight line distance L are the lengths when the portion in which the circumferential groove is defined by the dividing surface is projected onto a surface orthogonal to the tire radial direction.
[0011]
In the present invention, a pneumatic tire having a circumferential groove extending in the tire circumferential direction in the tread portion is manufactured by using a mold in which a portion where the tread portion is molded is divided into a plurality of portions through a division surface in the tire radial direction. In this case, since the path L ′ of the portion where the circumferential groove is defined by the dividing surface of the mold is made longer than the linear distance L, when the thin film is formed on the groove bottom of the circumferential groove, the thin film Will have a slack. Therefore, when a tensile force is applied to the thin film by the movement of the tread portion during tire traveling, the tensile force can be absorbed. Therefore, even when a thin film due to overflow is formed on the groove bottom of the circumferential groove, the occurrence of cracks in the thin film can be suppressed, and further the generation of cracks at the groove bottom can be suppressed.
[0012]
In the present invention, road L of the portion where the circumferential groove is defined by dividing plane 'is, 1.1 L ≦ L with respect to the straight line distance L' shall satisfy the relationship. Further, it is preferable that the amplitude d of the portion where the circumferential groove is partitioned by the dividing surface satisfies the relationship of 0.1 L ≦ d ≦ 0.5 L with respect to the linear distance L. Furthermore, the shape of the portion where the circumferential groove is partitioned by the dividing surface is preferably a curved shape, a wave shape, or a zigzag shape. Thereby, generation | occurrence | production of the crack in a thin film and generation | occurrence | production of the crack in a groove bottom can be suppressed more effectively.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.
[0014]
FIG. 1 shows a tread pattern of a pneumatic tire according to an embodiment of the present invention. In FIG. 1, the tread portion 1 is formed with a plurality of circumferential grooves 2 extending continuously in the tire circumferential direction and a plurality of sub-grooves 3 extending in the tire width direction. A block-shaped or rib-shaped land portion 4 is formed by the groove 3. The circumferential groove 2 may be linear or zigzag.
[0015]
FIG. 2 shows a tread molding portion of a tire mold for molding the pneumatic tire. As shown in FIG. 2, in the tire mold of the present embodiment, a portion where the tread portion 1 is formed is divided into a plurality through a division surface X in the tire radial direction. On the inner surfaces of the divided molds 11a and 11b (sectors), circumferential groove forming bones 12 and minor groove forming bones 13 are processed so as to correspond to the circumferential grooves 2 and the minor grooves 3 of the tire.
[0016]
Here, as shown in FIG. 3, the path L ′ where the circumferential groove 2 is partitioned by the dividing plane X is set longer than the linear distance L. In other words, as shown in FIG. 4, the path L ′ of the portion where the circumferential groove forming bone 12 corresponding to the circumferential groove 2 is divided by the dividing surface X is set longer than the linear distance L.
[0017]
In this way, using a mold in which a portion where the tread portion 1 is molded is divided into a plurality of portions via the division surface X in the tire radial direction, the tread portion 1 is provided with a circumferential groove 2 extending in the tire circumferential direction. When the tire is manufactured, a thin film due to overflow is formed at the groove bottom of the circumferential groove 2 by making the path L ′ of the portion where the circumferential groove 2 is defined by the dividing surface X of the mold longer than the linear distance L. If done, the film will have a slack. Therefore, even when a thin film due to overflow is formed on the groove bottom of the circumferential groove 2, it is possible to suppress the generation of cracks in the thin film and further to suppress the generation of cracks at the groove bottom.
[0018]
Circumferential grooves 2 road L portions partitioned by dividing plane X 'is, 1.1 L ≦ L with respect to the straight line distance L' shall satisfy the relationship. When this road L ′ is less than 1.1 L, the effect of suppressing the occurrence of cracks is insufficient.
[0019]
The amplitude d of the portion where the circumferential groove 2 is partitioned by the dividing surface X preferably satisfies the relationship of 0.1 L ≦ d ≦ 0.5 L with respect to the linear distance L. When the amplitude d is less than 0.1 L, the effect of suppressing the occurrence of cracks is insufficient. On the other hand, when the amplitude d exceeds 0.5 L, an effect of suppressing the generation of cracks can be obtained, but a thin film due to overflow is likely to be formed due to abrasion of the protruding portion.
[0020]
5 (a) to 5 (d) show the shape of the portion where the circumferential groove is partitioned by the dividing surface, that is, the shape of the portion where the circumferential groove forming bone corresponding to the circumferential groove is divided by the dividing surface. Various modifications are shown. As shown in FIGS. 5A to 5D, the shape of the portion where the circumferential groove 2 is partitioned by the dividing plane X is a curved shape or a wave shape including a single arch shape or a combination of a plurality of arch shapes. Or it can be zigzag-shaped.
[0021]
6 (a) to 6 (d) show various thin films formed on the groove bottom of the circumferential groove, and correspond to the divided shapes of FIGS. 5 (a) to 5 (d). As shown in FIGS. 6A to 6D, the thin film 5 formed by overflow on the groove bottom of the circumferential groove 2 has a slack, and has a tensile force generated by the movement of the tread portion 1 during tire rolling. It can be absorbed.
[0022]
【Example】
A pneumatic tire having a tire size of 275 / 70R22.5 and having a circumferential groove extending in the tire circumferential direction in the tread portion, and a section in which the tread portion is molded is divided into a plurality of portions through a division surface in the tire radial direction. When manufacturing using a mold of a type, the shape of the portion where the circumferential groove is defined by the dividing surface, the inclination angle of the portion with respect to the tire circumferential direction, the distance L ′ of the portion, and the amplitude d of the portion are varied. (Conventional Examples 1-2 , Comparative Example 1 and Examples 1-4 ).
[0023]
After vulcanizing a predetermined number of pneumatic tires using the molds of Conventional Examples 1 and 2 , Comparative Example 1 and Examples 1 to 4 , the occurrence of overflow at the groove bottom of the circumferential groove was examined. . When overflow occurred, the degree was evaluated in five levels. A larger value means more overflow.
[0024]
Furthermore, the pneumatic tires obtained in Conventional Examples 1 and 2 , Comparative Example 1 and Examples 1 to 4 are assembled to a wheel having a rim size of 22.5 × 7.50 and mounted on a vehicle under the condition of an air pressure of 900 kPa. After running, the occurrence of cracks in the thin film due to overflow and the occurrence of cracks at the groove bottom were investigated. The results are shown in Table 1.
[0025]
[Table 1]

[0026]
As can be seen from Table 1, in Examples 1 to 4 , even when a thin film due to overflow is formed on the groove bottom of the circumferential groove, the occurrence of cracks in the thin film is suppressed, and cracks at the groove bottom are prevented. Occurrence could be suppressed.
[0027]
【The invention's effect】
As described above, according to the present invention, a circumferential groove extending in the tire circumferential direction is formed in the tread portion using a mold in which a portion where the tread portion is molded is divided into a plurality through a division surface in the tire radial direction. When manufacturing the provided pneumatic tire, the distance L ′ of the portion where the circumferential groove is defined by the dividing surface of the mold is made longer than the linear distance L, and the distance of the portion where the circumferential groove is defined by the dividing surface Since L ′ satisfies the relationship of 1.1 L ≦ L ′ with respect to the linear distance L, even if a thin film due to overflow is formed on the groove bottom of the circumferential groove, generation of cracks in the thin film In addition, the occurrence of cracks at the groove bottom can be suppressed.
[Brief description of the drawings]
FIG. 1 is a plan view showing a tread pattern of a pneumatic tire according to an embodiment of the present invention.
FIG. 2 is a plan view showing a tread forming portion of a tire mold according to an embodiment of the present invention.
3 is an enlarged plan view showing a main part of a circumferential groove in FIG. 1. FIG.
4 is an enlarged plan view showing a main part of the circumferential groove forming bone in FIG. 2. FIG.
FIGS. 5A and 5B show circumferential groove-forming bones having different shapes, and FIGS. 5A to 5D are enlarged plan views of main parts, respectively. FIGS.
FIGS. 6A and 6B show groove bottom thin films obtained by circumferential groove-forming bones having different shapes, and FIGS. 6A to 6D are enlarged plan views of main parts, respectively. FIGS.
7A to 7C are explanatory views for explaining a mechanism of crack generation in a conventional pneumatic tire.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Tread part 2 Main groove 3 Sub groove 4 Land part 5 Thin film 11a, 11b Mold 12 Circumferential groove forming bone 13 Sub groove forming bone X Dividing surface

Claims (6)

In the pneumatic tire manufactured by the mold in which the tread portion includes a circumferential groove extending in the tire circumferential direction, and a portion where the tread portion is formed is divided into a plurality of portions through a division surface in the tire radial direction. The distance L ′ of the portion where the directional groove is defined by the dividing surface is made longer than the linear distance L, and the distance L ′ of the portion where the circumferential groove is defined by the dividing surface is 1 with respect to the linear distance L. A pneumatic tire that satisfies the relationship of 1L ≦ L ′ .   2. The pneumatic tire according to claim 1, wherein an amplitude d of a portion where the circumferential groove is partitioned by the dividing surface satisfies a relationship of 0.1 L ≦ d ≦ 0.5 L with respect to the linear distance L. 3. The pneumatic tire according to claim 1 or 2 , wherein a shape of a portion where the circumferential groove is partitioned by the dividing surface is a curved shape, a wave shape, or a zigzag shape. A mold for manufacturing a pneumatic tire provided with a circumferential groove extending in a tire circumferential direction in a tread portion, wherein a portion for forming the tread portion is divided into a plurality through a division surface in a tire radial direction. In the mold, the distance L ′ of the portion where the circumferential groove is defined by the dividing surface is longer than the linear distance L, and the distance L ′ of the portion where the circumferential groove is defined by the dividing surface is a linear distance. A tire mold that satisfies the relationship 1.1 L ≦ L ′ with respect to L. 5. The tire mold according to claim 4 , wherein an amplitude d of a portion where the circumferential groove is partitioned by the dividing surface satisfies a relationship of 0.1 L ≦ d ≦ 0.5 L with respect to the linear distance L. 6. The tire mold according to claim 4 or 5 , wherein a shape of a portion where the circumferential groove is partitioned by the dividing surface is a curved shape, a wave shape, or a zigzag shape.

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