JP4804886B2 - Tire bladder and tire manufacturing method - Google Patents

Description

  The present invention relates to a bladder used in a tire vulcanization / molding process.

  A mold containing a bladder is used in a vulcanization / molding process of a pneumatic tire. In the vulcanization / molding process, a pre-formed green tire is first put into an opened mold. When thrown, the bladder is contracted. When thrown, the bladder is positioned inside the green tire. Next, the bladder expands due to gas filling. This expansion causes the green tire to deform. This deformation is called shaping. Next, the mold is tightened. Next, the internal pressure of the bladder is increased. The green tire is pressed between the cavity surface of the mold and the outer surface of the bladder. The green tire is heated by heat conduction from the bladder. The rubber composition of the green tire flows by pressurization and heating. The rubber causes a crosslinking reaction by heating, and a tire is obtained.

  The bladder is made of a material suitable for repeated expansion and contraction. Specifically, the bladder is made of a crosslinked rubber. The hardness (JIS-A) of the bladder is approximately 65. The bladder is generally soft. A bladder for obtaining a high-quality tire is disclosed in Japanese Patent Application Laid-Open Nos. 5-131454 and 2005-41170.

  A green tire is obtained by preforming a plurality of types of rubber sheets into a cylindrical shape. As the rubber sheet, an inner liner ply, a carcass ply, a belt ply, a tread sheet or the like is used.

In the preforming step, the inner liner ply is wound around the preforming machine so that both ends thereof overlap. In the inner liner ply of the green tire, the thickness of the overlap portion is about twice that of the other portions. There is a step between the overlap portion and the other portion. This overlap portion is crushed by the bladder in the vulcanization / molding process. By crushing, an inner liner ply having a uniform thickness can be obtained.
JP-A-5-131454 JP-A-2005-41170

  As described above, since the bladder is soft, it may follow the step of the inner liner ply when expanded. When the bladder follows the step, sufficient crushing of the overlap portion is not achieved. When the bladder is along the step, the thickness of the inner liner ply of the tire is uneven.

  The carcass ply and the belt ply also have an overlap portion at the stage of the green tire. Insufficient crushing of the overlap portion will cause uneven thickness in the tire.

  In a tire having a non-uniform thickness, a thick portion may protrude more than other portions. This phenomenon is called “bulge”. When an internal pressure is applied to a tire having a non-uniform thickness, expansion of the thick portion is suppressed and the tire may be recessed more than other portions. This phenomenon is called “dent”. Bulge and dent impair the appearance of the tire.

  An object of the present invention is to provide a bladder from which a high-quality tire can be obtained.

  The tire bladder according to the present invention includes a high hardness portion. The hardness of the high hardness portion is 70 or more and 80 or less.

  Preferably, the bladder further includes a low hardness portion whose hardness is lower than that of the high hardness portion. This high hardness portion exists at a position corresponding to the joint portion of the tire ply. Preferably, the ratio of the width of the high hardness portion existing at the position corresponding to the joint portion to the overlap width of the ply in the joint portion is 100% or more and 300% or less. Preferably, the difference between the hardness of the high hardness portion and the hardness of the low hardness portion is 5 or more.

The tire manufacturing method according to the present invention includes:
(1) A step of putting a green tire into a mold having a high hardness portion and containing a bladder having a hardness of 70 to 80 in the high hardness portion;
(2) a step in which the bladder expands, and (3) a step in which the green tire is pressurized and heated between the cavity surface of the mold and the bladder, and the joint portion of the green tire is pressed by the high hardness portion.

  In the bladder according to the present invention, the high hardness portion crushes the joint portion. By using this bladder, a tire excellent in quality can be obtained.

  Hereinafter, the present invention will be described in detail based on preferred embodiments with appropriate reference to the drawings.

  FIG. 1 is a cross-sectional view showing a bladder 2 according to an embodiment of the present invention. FIG. 1 shows a cross section along a plane including an axis. The bladder 2 is obtained by crosslinking the rubber composition. The bladder 2 includes a main body 4 and a pair of clamps 6. The main body 4 is cylindrical. The clamp 6 has a ring shape. The clamps 6 are located at the upper end and the lower end of the main body 4.

  FIG. 2 is a cross-sectional view along a plane perpendicular to the axis, showing the body 4 of the bladder 2 of FIG. The main body 4 includes a high hardness portion 8 and a low hardness portion 10. The high hardness portion 8 and the low hardness portion 10 are adjacent to each other in the circumferential direction. The high hardness portion 8 extends from the upper end to the lower end of the main body 4. The low hardness portion 10 also extends from the upper end to the lower end of the main body 4. In FIG. 2, what is indicated by a double-headed arrow W <b> 1 is the width of the high hardness portion 8. As is clear from FIG. 1, the clamp 6 is made of a material equivalent to the low hardness portion 10.

  The bladder 2 is used by being housed in a mold. In the tire manufacturing method using this bladder 2, first, a green tire obtained by preforming is put into the mold in a state where the mold is open and the bladder 2 is contracted. Next, the bladder 2 is expanded by being filled with gas. As the bladder 2 expands, the green tire deforms. Next, the mold is tightened. Next, the internal pressure of the bladder 2 increases. The green tire is pressed against the cavity surface of the mold by the bladder 2 and pressurized. Along with the pressurization, the green tire is heated. The rubber composition flows along the cavity surface by pressurization and heating. Further heating causes the rubber to undergo a crosslinking reaction, and a tire is obtained.

  FIG. 3 is a schematic view showing the main body 4 of the bladder 2 of FIG. 2 together with the inner liner ply 12 of the green tire. In FIG. 3, the positional relationship between the main body 4 and the inner liner ply 2 is schematically shown. The inner liner ply 12 includes a joint portion 14. In the joint portion 14, one end and the other end of the inner liner ply 12 overlap each other. In FIG. 3, what is indicated by W <b> 2 is the overlap width of the joint portion 14. Due to the overlap, a step is generated in the inner liner ply 12.

  As is clear from FIG. 3, the high hardness portion 8 exists at a position corresponding to the joint portion 14. As the bladder 2 expands, the high hardness portion 8 presses the joint portion 14. Since the high hardness portion 8 is difficult to follow along the step, the joint portion 14 is sufficiently crushed by the high hardness portion 8. By crushing, the thickness of the joint part 14 approaches the thickness of the other part. With this bladder 2, a tire having excellent homogeneity can be obtained.

  The hardness H1 of the high hardness portion 8 is 70 or more and 80 or less. By setting the hardness H1 to be 70 or more, the joint portion 14 is sufficiently crushed. In this respect, the hardness H1 is more preferably equal to or greater than 72, and particularly preferably equal to or greater than 74. The bladder 2 having a hardness H1 of 80 or less is excellent in durability. From the viewpoint of durability, the hardness H1 is more preferably 78 or less, and particularly preferably 76 or less. In the present invention, the hardness is measured by a type A durometer in accordance with the provisions of “JIS K6253”.

  The hardness H2 of the low hardness portion 10 is 68 or less. The low hardness portion 10 contributes to the durability of the bladder 2. In this respect, the hardness H2 is more preferably 66 or less, and particularly preferably 65 or less. The hardness H2 is preferably 62 or more.

  From the viewpoint of coexistence of the advantages of the high hardness portion 8 and the low hardness portion 10, the difference (H1−H2) between the hardness H1 of the high hardness portion 8 and the hardness H2 of the low hardness portion 10 is preferably 5 or more, more preferably 7 or more. preferable. The difference (H1-H2) is preferably 15 or less.

The hardness difference between the high hardness part 8 and the low hardness part 10 is
(1) A base polymer different from the base polymer of the low-hardness part is used for the high-hardness part (2) Many crosslinking agents (for example, sulfur) are blended in the high-hardness part (3) High-hardness part (4) A large amount of reinforcing agent (for example, carbon black) is blended in the high hardness part.

  From the viewpoint that the joint portion 14 is sufficiently crushed, the ratio of the width W1 of the high hardness portion 8 to the overlap width W2 is preferably 100% or more, and more preferably 150% or more. From the viewpoint of durability of the bladder 2, the ratio of the width W1 to the width W2 is preferably 300% or less, and more preferably 250% or less.

  In the green tire, one end of the joint portion of the carcass ply overlaps the other end. In the green tire, one end of the belt ply may overlap the other end. The high hardness portion 8 may be disposed at a position corresponding to these joint portions. These joint portions are sufficiently crushed by the high hardness portion 8. By crushing the joint portion 14, a tire having excellent uniformity can be obtained.

  In a green tire, one end of the joint portion of the tread sheet is abutted against the other end. In the green tire, one end of the side wall sheet is also abutted against the other end of the joint portion of the sidewall sheet. The high hardness portion 8 may be disposed at a position corresponding to these joint portions. The joined part is sufficiently pressurized by the high hardness part 8. Sufficient pressurization contributes to the bonding strength between one end and the other end.

  FIG. 4 is a cross-sectional view along a plane perpendicular to the axis, showing a bladder 16 according to another embodiment of the present invention. In FIG. 4, the main body 18 of the bladder 16 is shown. Although not shown, the bladder 16 includes a clamp similar to the bladder 2 shown in FIG.

  The main body 18 includes three high hardness portions 20 and three low hardness portions 22. These high hardness portions 20 and low hardness portions 22 are alternately arranged in the circumferential direction. These high hardness parts 20 are located at equal intervals. Specifically, the high hardness part 20 is arrange | positioned every 120 degrees by a central angle. The high hardness portion 20 extends from the upper end to the lower end of the main body 18. The low hardness portion 22 also extends from the upper end to the lower end of the main body 18. The material of the high hardness portion 20 is the same as that of the high hardness portion 8 of the bladder 2 shown in FIG. The material of the low hardness portion 22 is the same as that of the low hardness portion 10 of the bladder 2 shown in FIG.

  FIG. 5 is a schematic view showing the main body 18 of the bladder 16 of FIG. 4 together with the green tire 24. 5, the positional relationship among the main body 18, the inner liner ply 12, the carcass ply 26, and the belt ply 28 is schematically shown. The inner liner ply 12 includes a joint portion 14. In the joint portion 14, one end and the other end of the inner liner ply 12 overlap each other. Due to the overlap, a step is generated in the inner liner ply 12. The carcass ply 26 includes a joint portion 30. In the joint portion 30, one end and the other end of the carcass ply 26 overlap each other. Due to the overlap, a step is generated in the carcass ply 26. The belt ply 28 includes a joint portion 32. In the joint portion 32, one end and the other end of the belt ply 28 overlap each other. Due to the overlap, a step is generated in the belt ply 28.

  As is clear from FIG. 5, the first high hardness portion 20 a exists at a position corresponding to the joint portion 14 of the inner liner ply 12. As the bladder 16 expands, the first high hardness portion 20 a presses the joint portion 14 of the inner liner ply 12. Since the first high hardness portion 20a is difficult to follow along the step, the joint portion 14 is sufficiently crushed by the first high hardness portion 20a. The second high hardness portion 20 b exists at a position corresponding to the joint portion 30 of the carcass ply 26. As the bladder 16 expands, the second high hardness portion 20 b presses the joint portion 30 of the carcass ply 26 via the inner liner ply 12. The joint portion 30 is sufficiently crushed by the second high hardness portion 20b. The third high hardness portion 20 c is present at a position corresponding to the joint portion 32 of the belt ply 28. As the bladder 16 expands, the third high hardness portion 20 c presses the joint portion 32 of the belt ply 28 via the inner liner ply 12 and the carcass ply 26. The joint portion is sufficiently crushed by the third high hardness portion 20c. With this bladder 16, a tire having excellent uniformity can be obtained.

  Also in this bladder 16, the ratio of the width of the high hardness portion 20 to the overlap width of the joint portions 14, 30, 32 is preferably 100% or more, and more preferably 150% or more. The ratio of the width of the high hardness portion 20 to the overlap width of the joint portions 14, 30, 32 is preferably 300% or less, and more preferably 250% or less.

  FIG. 6 is a cross-sectional view along a plane perpendicular to the axis, showing a bladder 34 according to still another embodiment of the present invention. In FIG. 6, the main body 36 of the bladder 34 is shown. Although not shown, the bladder includes a clamp 6 similar to the bladder 2 shown in FIG. The main body 36 consists only of the high hardness portion 38. The material of the high hardness portion 38 is the same as that of the high hardness portion 8 of the bladder 2 shown in FIG.

  When the bladder 34 expands, the main body 36 presses the joint portion. Since the main body is composed only of the high hardness portion 38, the joint portion is sufficiently crushed. With this bladder 34, a tire having excellent uniformity can be obtained.

  Hereinafter, the effects of the present invention will be clarified by examples. However, the present invention should not be construed in a limited manner based on the description of the examples.

[Experiment 1]
[Example 1]
The rubber composition was crosslinked to produce a bladder having the shape shown in FIG. The main body of this bladder consists only of a high hardness part. The hardness H1 of this high hardness part is 75. Using this bladder, a green tire was pressurized and heated to obtain a tire. The green tire includes an inner liner ply, a carcass ply, and a belt ply. These plies have an overlap portion. The size of this tire is 205 / 55R16.

[Examples 2 to 5 and Comparative Examples 1 to 2]
The bladders of Examples 2 to 5 and Comparative Examples 1 to 2 were obtained in the same manner as in Example 1 except that the rubber composition of the high hardness part was changed and the hardness H1 was as shown in Table 1 below. . A tire was obtained using this bladder.

[Evaluation of homogeneity]
The tire was mounted on a rim of “16 × 6.5JJ”, and the tire was filled with air so that the internal pressure was 200 kPa. While applying a load of 4.33 kN to this tire, ROA, R1H, RRO and RRO1H were measured using a uniformity measuring device. Measurements were made on 30 tires, and the average value and σ were calculated. The results are shown in Table 1 below.

[Evaluation of appearance]
The appearance of the tire was visually observed, and the degree of bulge and dent was rated. The results are shown in Table 1 below. The larger the value, the better the appearance.

[Evaluation of durability]
A bladder was incorporated into the mold and the expansion and contraction were repeated. The number of expansions until breakage was counted. This result is shown in Table 1 below as an index when Comparative Example 1 is set to 100.

  As shown in Table 1, the tires of the examples are excellent in homogeneity and appearance. From this evaluation result, the superiority of the present invention is clear.

[Experiment 2]
[Example 6]
The rubber composition was crosslinked to produce a bladder having the shape shown in FIG. The body of this bladder consists of a high hardness part and a low hardness part. The hardness H1 of the high hardness portion is 75, and the hardness H2 of the low hardness portion is 68. Using this bladder, a green tire was pressurized and heated to obtain a tire. The green tire includes an inner liner ply, a carcass ply, and a belt ply. These plies have an overlap portion. In the pressurization and heating of the green tire, the bladder was set in the mold so that the high hardness portion existed at a position corresponding to the overlap portion of the inner liner ply. The ratio of the width W1 of the high hardness portion to the overlap width W2 of the inner liner ply is 250%. The size of this tire is 205 / 55R16.

[Examples 7 to 8]
The bladders of Examples 7 and 8 were obtained in the same manner as in Example 1 except that the rubber composition of the high hardness part was changed and the hardness H1 was as shown in Table 2 below. A tire was obtained using this bladder.

[Examples 9 to 11]
The bladders of Examples 9 to 11 were obtained in the same manner as Example 1 except that the width W1 of the high hardness part was changed. A tire was obtained using this bladder.

[Example 12]
The rubber composition was crosslinked to produce a bladder having the shape shown in FIG. The body of this bladder consists of three high hardness parts and three low hardness parts. The hardness H1 of the high hardness portion is 75, and the hardness H2 of the low hardness portion is 68. Using this bladder, a green tire was pressurized and heated to obtain a tire. The green tire includes an inner liner ply, a carcass ply, and a belt ply. These plies have an overlap portion. In the pressurization and heating of the green tire, the bladder was set in the mold so that the high hardness portion exists at a position corresponding to each overlap portion. The ratio of the width of the high hardness portion to the overlap width of each ply is 250%. The size of this tire is 205 / 55R16.

[Evaluation of appearance]
The appearance of the tire was visually observed, and the degree of bulge and dent was rated. The results are shown in Table 2 below. The larger the value, the better the appearance.

  As shown in Table 2, the tires of the examples are excellent in homogeneity and appearance. From this evaluation result, the superiority of the present invention is clear.

  The bladder according to the present invention can be used for manufacturing various tires.

FIG. 1 is a cross-sectional view illustrating a bladder according to an embodiment of the present invention. 2 is a cross-sectional view along the plane perpendicular to the axis, showing the body of the bladder of FIG. FIG. 3 is a schematic view showing the body of the bladder of FIG. 2 together with the inner liner ply of the green tire. FIG. 4 is a cross-sectional view along a plane perpendicular to the axis, showing a bladder according to another embodiment of the present invention. FIG. 5 is a schematic view showing the body of the bladder of FIG. 4 together with a green tire. FIG. 6 is a cross-sectional view along a plane perpendicular to the axis, showing a bladder according to still another embodiment of the present invention.

Explanation of symbols

2, 16, 34 ... Bladder 4 ... Main body 6 ... Clamp 8, 20, 20a, 20b, 20c, 38 ... High hardness part 10,22 ... Low hardness part 12 ... Inner Liner ply 14, 30, 32 ... Joint part 24 ... Green tire 26 ... Carcass ply 28 ... Belt ply 36 ... Body

Claims (3)

Than high hardness section and the high-hardness portion is provided with a low hardness low hardness section, Ri 80 der less hardness (JIS-A) 70 or more of the high hardness section,
This high hardness part exists in a position corresponding to the joint part of the tire ply,
The difference between the hardness of the hardness and low hardness of the high hardness section, bladders Ru der 5 or more tires. 2. The bladder according to claim 1 , wherein a ratio of a width of a high hardness portion existing at a position corresponding to the joint portion to an overlap width of a ply in the joint portion is 100% or more and 300% or less. High hardness section and the hardness than the high-hardness portion is provided with a lower low hardness section and the hardness of the high hardness section Ri der 70 to 80. The high hardness portion corresponds to the joint portion of the ply tire position being present, into a mold difference Ru der 5 or bladder is accommodated between the hardness of the hardness and low hardness of the high hardness section, the step of the green tire is turned,
A tire manufacturing method including a step of expanding the bladder and a step of pressing and heating the green tire between a cavity surface of the mold and the bladder, and pressing a joint portion of the green tire by a high hardness portion.

Images