JP5000276B2 - Pneumatic tire manufacturing method - Google Patents

Description

  The present invention relates to a method for manufacturing a pneumatic tire.

  The tire is obtained from a green tire. In this green tire, a large number of rubber members are laminated. Specific examples of the rubber member include an inner liner, a carcass ply, a sidewall rubber sheet, a belt ply, and a tread rubber sheet. The green tire is pressurized and heated in a mold. The rubber composition of a green tire flows by pressurization and heating. By heating, a crosslinking reaction occurs in the rubber composition. This process is called a vulcanization process.

  When green tires are molded, air may be caught in the green tires. This air exists between the rubber member and another rubber member. The air moves due to the flow of the rubber composition in the vulcanization process. By this movement, air can be discharged out of the green tire. However, if the movement is insufficient, air remains in the tire and an air pool is formed.

  Air pockets impair tire quality. For example, if air remains between the carcass ply and the sidewall, wrinkles are generated on the sidewall. Sidewalls with scissors are repaired. Repair takes time and effort. In addition, the residual air impairs the tire uniformity.

JP-A-2006-51711 discloses a tire manufacturing method that can suppress the formation of air pockets. In this manufacturing method, a rubber strip is used. The rubber strip is provided with a plurality of exhaust grooves that facilitate air movement.
JP 2006-51711 A

  In order to prevent the formation of an air reservoir in the tire, the tire may be manufactured using a rubber sheet for a sidewall in which a portion corresponding to a portion where the air easily accumulates is locally thickened. In this case, the air existing between the carcass ply and the sidewall can be pushed out in the vulcanization process. In this tire, no air pool is formed. However, this tire causes an increase in tire mass.

  A tire suitable for the size of the vehicle is attached to the vehicle. For this reason, tires of various sizes are prepared. The tire includes a pair of sidewalls. In order to manufacture a tire, an optimum size rubber sheet for a sidewall is prepared for each tire size. The site where the air pool is formed varies depending on the tire size. When the formation of the air pocket is suppressed as described above, the locally thickened portion of the rubber sheet can be changed for each tire size. For this reason, one size rubber sheet cannot be used for a plurality of tires having different sizes. In order to prevent the formation of air pockets, this rubber sheet must be prepared for each tire size. In a mass production factory, it is difficult to prepare this rubber sheet for each size of tire to be manufactured. This manufacturing method causes an increase in manufacturing cost.

  In order to suppress the formation of an air pool, a carcass ply in which holes are formed by holing may be used. In this case, this hole may remain in the tire.

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

A method for manufacturing a pneumatic tire according to the present invention includes:
(1) A step of forming a rubber sheet for a sidewall having a protrusion extending in the extrusion direction on its back surface using a die having a groove at its discharge port;
(2) a step of obtaining a green tire by attaching the rubber sheet to the carcass ply so that the back surface is in contact with the carcass ply;
(3) including a step of pressing and heating the green tire in a mold.

  Preferably, in this manufacturing method, the discharge port includes a large number of the grooves. These grooves are arranged in the width direction. The pitch of these grooves is 2.5 mm or more and 3.5 mm or less.

  Preferably, in this manufacturing method, the cross-sectional shape of the groove is a semicircle. The radius of this circle is not less than 0.55 mm and not more than 0.65 mm.

  Preferably, in this manufacturing method, the number of the grooves is 18 or more and 21 or less.

  The pneumatic tire according to the present invention includes a step of forming a rubber sheet for a sidewall having a protrusion extending in the extrusion direction on the back surface thereof using a base having a groove at the discharge port, and the back surface is a carcass. A pneumatic tire including a step of attaching a rubber sheet to a carcass ply so as to contact a ply to obtain a green tire, and a step of pressing and heating the green tire in a mold. Obtained by the manufacturing method.

  In this manufacturing method, protrusions are provided on the back surface of the rubber sheet for the sidewall. For this reason, in the green tire molding process, the air between the rubber sheet and the carcass ply can move along the ridges. This movement prompts the discharge of air. In this manufacturing method, air remaining between the rubber sheet and the carcass ply can move along the ridges in the vulcanization process of the green tire. This movement effectively disperses the air. In the tire manufactured in this way, formation of an air pocket can be prevented. With this manufacturing method, a high-quality tire can be obtained. In this manufacturing method, since formation of an air reservoir is prevented, it is not necessary to prepare a rubber sheet for a sidewall in which the portion where the thickness is increased is locally changed for each tire size. This manufacturing method can be applied to a mass production factory. In the tire manufactured by this manufacturing method, the tire mass can be maintained. Since no holing is required, the quality of the tire manufactured by this manufacturing method is high.

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

  FIG. 1 is a front view showing a base 2 used in a method for manufacturing a pneumatic tire according to an embodiment of the present invention. The base 2 includes a die plate 4, a holder 6, and a discharge port 8. Although not shown, the die 2 is attached to the head of the extruder. This extruder forms a rubber sheet for a sidewall while extruding the rubber composition.

  The die plate 4 is a substantially rectangular plate. In this manufacturing method, the die plate 4 constitutes the upper part of the base 2. The die plate 4 has a recess 10 on its lower side. The die plate 4 is hard chrome plated.

  The holder 6 is a substantially rectangular plate. In this manufacturing method, the holder 6 constitutes the lower part of the base 2. The holder 6 is hard chrome plated.

  The discharge port 8 discharges the rubber composition for sidewalls charged into the extruder. The discharge port 8 has a rectangular shape. In this manufacturing method, the discharge port 8 is formed by combining the die plate 4 and the holder 6. The discharge port 8 includes a ridge forming portion 12. The ridge forming portion 12 is provided on a part of the lower surface 14 of the discharge port 8. The ridge forming portion 12 may be provided on the entire lower surface 14.

  The ridge forming portion 12 includes a large number of grooves 16. In other words, the discharge port 8 includes a large number of grooves 16. In this manufacturing method, the number of the grooves 16 is 18. These grooves 16 are arranged at equal intervals in the width direction. These grooves 16 extend along the extrusion direction. The cross-sectional shape of the groove 16 is a semicircle.

  FIG. 2 is an enlarged perspective view showing a part of the rubber sheet 18 for the sidewall formed by the extruder provided with the base 2 of FIG. The rubber sheet 18 has a front surface 20 and a back surface 22. In FIG. 2, the back surface 22 of the rubber sheet 18 is shown facing up. In FIG. 2, the arrow line A is an extrusion direction. As illustrated, the rubber sheet 18 includes a plurality of ridges 24 on the back surface 22 thereof. The ridges 24 extend in the extrusion direction. The cross-sectional shape of the ridge 24 is a semicircle.

  In this manufacturing method, the rubber composition for sidewalls is put into an extruder having a base 2 attached to the head. The rubber composition is discharged as a rubber sheet 18 from the discharge port 8 of the base 2 while being extruded by the extruder. As described above, since the shape of the discharge port 8 is rectangular, the cross-sectional shape of the rubber sheet 18 is also rectangular. In this manufacturing method, the rubber composition is extruded while being in contact with the groove 16. Due to the groove 16, the rubber sheet 18 is formed with a ridge 24 extending in the extrusion direction. In this manufacturing method, the surface of the rubber sheet 18 on which the ridges 24 are formed is the back surface 22. In this manufacturing method, the rubber sheet 18 for sidewalls is formed using the die 2 having the groove 16 at the discharge port 8, and the convex surface 24 extending in the extrusion direction on the back surface 22. As described above, since the cross-sectional shape of the groove 16 is a semicircle, the cross-sectional shape of the ridge 24 is also a semicircle. In addition, since this rubber sheet 18 is not yet vulcanized, it sticks and does not leave when it comes into direct contact with another rubber sheet 18 in a stockpiling process or a conveying process. Although not shown, a film made of a thermoplastic resin such as polyethylene and polypropylene is in close contact with the rubber sheet 18 formed by the extruder. This film prevents the rubber sheet 18 from coming into direct contact with another rubber sheet 18. In this manufacturing method, the film is adhered to the back surface 22 of the rubber sheet 18.

  Next, after the film is peeled off, the rubber sheet 18 is supplied to the former. Other rubber members are also supplied to the former. Examples of the other rubber member include an inner liner, a carcass ply, a belt ply, and a tread rubber sheet 18. These rubber members are assembled in the former to obtain a green tire. The process for obtaining this green tire is referred to as a molding process.

  In this manufacturing method, in the molding process, the rubber sheet 18 is laminated on the carcass ply while the former rotates. The rubber sheet 18 is affixed to the carcass ply so that the back surface 22 of the rubber sheet 18 contacts the carcass ply. Although not shown, the tip of the ridge 24 of the rubber sheet 18 contacts the carcass ply. In this manufacturing method, in the molding step, the ridges 24 are arranged in the vicinity of a portion corresponding to an apex of a bead provided on the tire.

  Next, the green tire is subjected to a vulcanization process. In the vulcanization process, a green tire is put into a mold. The green tire is pressurized and heated with a mold and a bladder. The rubber composition flows by pressurization and heating. The ridge 24 is crushed by this flow. The rubber causes a crosslinking reaction by heating, and a tire is obtained.

  FIG. 3 is a cross-sectional view showing a part of a pneumatic tire 26 manufactured using the sidewall rubber sheet 18 of FIG. In FIG. 3, the vertical direction is the radial direction, the horizontal direction is the axial direction, and the direction perpendicular to the paper surface is the circumferential direction. The tire 26 has a substantially bilaterally symmetric shape with the one-dot chain line CL in FIG. 3 as the center. This alternate long and short dash line CL represents the equator plane of the tire 26. The tire 26 includes a tread 28, a sidewall 30, a bead 32, a carcass 34, a belt 36, an inner liner 38, and a chafer 40. The tire 26 is a tubeless type. The tire 26 is attached to a passenger car.

  The tread 28 is made of a crosslinked rubber having excellent wear resistance. The tread 28 has a shape protruding outward in the radial direction. The tread 28 includes a tread surface 42. The tread surface 42 is in contact with the road surface. A groove 44 is carved on the tread surface 42. The groove 44 forms a tread pattern. The groove 44 may not be cut in the tread 28.

  The sidewall 30 extends substantially inward in the radial direction from the end of the tread 28. The sidewall 30 is made of a crosslinked rubber. The sidewall 30 absorbs an impact from the road surface by bending. Furthermore, the sidewall 30 prevents the carcass 34 from being damaged.

  The bead 32 is located substantially inward of the sidewall 30 in the radial direction. The bead 32 includes a core 46 and an apex 48 that extends radially outward from the core 46. The core 46 has a ring shape. The core 46 includes a plurality of non-stretchable wires (typically steel wires). The apex 48 is tapered outward in the radial direction. The apex 48 is made of a highly hard crosslinked rubber.

  The carcass 34 includes a carcass ply 50. The carcass ply 50 is bridged between the beads 32 on both sides, and extends along the inside of the tread 28 and the sidewall 30. The carcass ply 50 is folded around the core 46 from the inner side to the outer side in the axial direction.

  Although not shown, the carcass ply 50 includes a large number of cords arranged in parallel and a topping rubber. The absolute value of the angle formed by each cord with respect to the equator plane is usually 70 ° to 90 °. In other words, the carcass 34 has a radial structure. The cord is usually made of organic fibers. Examples of preferable organic fibers include polyester fibers, nylon fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers. A carcass 34 having a bias structure may be employed.

  The belt 36 is located on the radially outer side of the carcass 34. The belt 36 is laminated with the carcass 34. The belt 36 reinforces the carcass 34. The belt 36 includes an inner ply 52 and an outer ply 54. Although not shown, each of the inner ply 52 and the outer ply 54 includes a large number of cords arranged in parallel and a topping rubber. Each cord is inclined with respect to the equator plane. The absolute value of the tilt angle is not less than 10 ° and not more than 35 °. The cord inclination direction of the inner ply 52 is opposite to the cord inclination direction of the outer ply 54. The inner ply 52 and the outer ply 54 constitute a so-called cross ply structure. A preferred material for the cord is steel. An organic fiber may be used for the cord.

  The inner liner 38 is joined to the inner peripheral surface of the carcass 34. The inner liner 38 is made of a crosslinked rubber. The inner liner 38 is made of rubber having excellent air shielding properties. The inner liner 38 plays a role of maintaining the internal pressure of the tire 26.

  The chafer 40 is located in the vicinity of the bead 32. When the tire 26 is incorporated into the rim, the chafer 40 comes into contact with the rim. By this contact, the vicinity of the bead 32 is protected. The chafer 40 is usually made of cloth and rubber impregnated in the cloth. A chafer 40 made of a single rubber may be used.

  As described above, in this manufacturing method, a large number of ridges 24 are provided on the back surface 22 of the rubber sheet 18 for the sidewall 30. For this reason, in the green tire molding process, the air between the rubber sheet 18 and the carcass ply 50 can move along the ridges 24. This movement prompts the discharge of this air.

  In this manufacturing method, air remaining between the rubber sheet 18 and the carcass ply 50 can move along the ridges 24 in the vulcanization process of the green tire. This movement effectively disperses the air. No air pool is formed in the tire 26 manufactured in this way. With this manufacturing method, a high-quality tire 26 can be obtained.

  As will be described later, in this manufacturing method, the position of the ridge forming portion 12 is appropriately determined in consideration of the location where the air pool of the tire 26 is formed. In this manufacturing method, the number, size, pitch, and the like of the grooves 16 provided in the ridge forming portion 12 are appropriately determined in consideration of the formation state of the air pool. In the rubber sheet 18 formed by the base 2 provided with such a ridge forming portion 12, the movement of air along the ridge 24 is easy. In this manufacturing method, formation of an air pool can be reliably prevented. In the rubber sheet 18, the side wall 30 is not wrinkled. The tire 26 manufactured by this manufacturing method is of high quality.

  In this manufacturing method, since formation of an air pool is prevented, it is not necessary to prepare the rubber sheet 18 for the sidewall 30 in which the portion where the thickness is increased is locally changed for each size of the tire 26. This manufacturing method can be applied to a mass production factory. In the tire 26 manufactured by this manufacturing method, the tire mass can be maintained. Since the holing is unnecessary, the quality of the tire 26 manufactured by this manufacturing method is high.

  In FIG. 1, the double arrow line WP represents the pitch of the grooves 16. The arrow line R represents the radius of the groove 16.

  In this manufacturing method, the pitch WP of the grooves 16 is preferably 2.5 mm or more and 3.5 mm or less. By setting this pitch to 2.5 mm or more, in the rubber sheet 18, the distance between the ridge 24 and another ridge 24 can be appropriately maintained. For this reason, the movement of the air existing between the sidewall 30 and the carcass 34 is urged. In this manufacturing method, formation of an air pool can be reliably prevented. Wrinkles are not generated on the sidewall 30 of the tire 26. With this manufacturing method, a high-quality tire 26 can be obtained. In this respect, the pitch is more preferably equal to or greater than 3.0 mm. By setting the pitch to 3.5 mm or less, the air dispersion effect along the ridges 24 can be maintained. In this manufacturing method, no air pool is formed in the tire 26. The tire 26 obtained by this manufacturing method is of high quality. From this viewpoint, the pitch is more preferably 3.2 mm or less.

  In this manufacturing method, the radius R of the groove 16 is preferably not less than 0.55 mm and not more than 0.65 mm. By setting the depth of the groove 16 to be 0.55 mm or more, the air dispersion effect along the ridges 24 can be maintained. In this manufacturing method, no air pool is formed in the tire 26. The tire 26 obtained by this manufacturing method is of high quality. From this viewpoint, the radius of the groove 16 is more preferably 0.60 mm or more. By setting the radius of the groove 16 to 0.65 mm or less, the movement of the air existing between the sidewall 30 and the carcass 34 is promoted. In this manufacturing method, formation of an air pool can be reliably prevented. Wrinkles are not generated on the sidewall 30 of the tire 26. With this manufacturing method, a high-quality tire 26 can be obtained. From this viewpoint, the radius of the groove 16 is more preferably 0.63 mm or less. When the cross-sectional shape of the groove 16 is defined by the width and depth, the width of the groove 16 is preferably 1.1 mm or more, and more preferably 1.15 mm or more. The width of the groove 16 is preferably 1.3 mm or less, and more preferably 1.20 mm or less. The depth of the groove 16 is preferably 0.55 mm or more, and more preferably 0.60 mm or more. The depth of the groove 16 is preferably 0.65 mm or less, and more preferably 0.63 mm or less.

  In this manufacturing method, the number of the grooves 16 provided in the ridge forming portion 12 is 18 or more from the viewpoint that air effectively moves along the ridges 24 and formation of an air pool can be reliably prevented. preferable. From the viewpoint that air dispersion can be appropriately maintained, the number of grooves 16 is preferably 21 or less. The tire 26 obtained by this manufacturing method is of high quality.

  As described above, in this manufacturing method, the position of the ridge forming portion 12 is appropriately determined in consideration of the location where the air pool of the tire 26 is formed. In FIG. 1, the point P <b> 1 represents one end of the lower surface 14 of the discharge port 8. A point P2 represents the other end of the lower surface 14. Point P3 represents one end of the ridge forming portion 12. A point P4 represents the other end of the ridge forming portion 12. A double arrow line WA represents the length from one end P1 to the other end P2. This length WA is the width of the discharge port 8. A double arrow line WB represents a length from one end P3 to the other end P4. This length WB is the width of the ridge forming portion 12. A double arrow line WC represents a length from one end P1 to one end P3. The position of one end P3 in the discharge port 8 is defined by the length WC. In this manufacturing method, the ridge forming portion 12 is shown in a range sandwiched between the left and right grooves 16 positioned outside in the width direction of the discharge port 8.

  In this manufacturing method, from the viewpoint that the formation of an air pool in the tire 26 can be effectively suppressed. The ratio of the width WB of the ridge forming portion 12 to the width WA of the discharge port 8 is preferably 15% or more. More preferably, it is 20% or more. This ratio is preferably 50% or less in order to reduce the processing cost for providing the groove 16 in the discharge port 8. In this manufacturing method, this ratio is 23%.

  In this manufacturing method, from the viewpoint that the formation of an air pool in the tire 26 can be effectively suppressed. The ratio of the length WC to the width WA of the discharge port 8 is preferably 30% or less. More preferably, it is 20% or less. In this manufacturing method, this ratio is 18%. The lower limit of this ratio is 0% because one end P1 of the discharge port 8 coincides with one end P3 of the ridge forming portion 12.

  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.

[Example 1]
A pneumatic tire of Example 1 is obtained from a rubber sheet for a sidewall having a basic configuration shown in FIG. 1 and formed by using a die having a ridge forming portion having the specifications shown in Table 1 below. It was. The pitch of the grooves of the protruding line forming portion is 3.0 mm. The cross-sectional shape of this groove is a semicircle, and the radius of this circle is 0.60 mm. The number of grooves is 18. In the green tire, the rubber sheet is disposed so that the back surface on which the ridges are provided is located on the carcass ply side.

[Examples 4, 5, 7, and 8]
A tire was obtained in the same manner as in Example 1 except that the groove radius was as shown in Tables 1 and 2 below.

[Examples 2, 3, 9 and 10]
A tire was obtained in the same manner as in Example 1 except that the groove pitch was as shown in Tables 1 and 2 below.

[Example 6]
A tire was obtained in the same manner as in Example 1 except that the number of grooves was as shown in Table 2 below.

[Comparative Example 1]
A tire was obtained from a rubber sheet for a sidewall formed using a conventional base.

[Evaluation]
When 200 prototype tires were prototyped, the occurrence of air accumulation and wrinkles was visually confirmed. The evaluation results are shown in Tables 1 and 2 as index values with the result of Comparative Example 1 being 100. It is shown that the smaller this value is, the better.

  As shown in Tables 1 and 2, in the examples, the occurrence of air accumulation and wrinkles is suppressed. From this evaluation result, the superiority of the present invention is clear.

  The pneumatic tire manufacturing method according to the present invention can be applied to various tire manufacturing methods.

FIG. 1 is a front view showing a base used in a method for manufacturing a pneumatic tire according to an embodiment of the present invention. FIG. 2 is an enlarged perspective view showing a part of a rubber sheet for a side wall formed by an extruder equipped with the die shown in FIG. FIG. 3 is a cross-sectional view showing a part of a pneumatic tire manufactured using the rubber sheet for a sidewall shown in FIG.

Explanation of symbols

2 ... Die plate 4 ... Die plate 6 ... Holder 8 ... Discharge port 10 ... Recess 12 ... Projection forming part 14 ... Lower surface 16, 44 ... Groove 18 ...・ Rubber sheet 20 ... surface 22 ... back surface 24 ... projection 26 ... tyre 28 ... tread 30 ... side wall 32 ... bead 34 ... carcass 36 ... belt 38 ... Inner liner 40 ... Chafer 42 ... Tread surface 46 ... Core 48 ... Apex 50 ... Carcass ply 52 ... Inner ply 54 ... Outer ply

Claims (2)

A step of forming a rubber sheet for a sidewall including a protrusion extending in the extrusion direction on the back surface thereof using a die having a groove at the discharge port,
The rubber sheet is attached to the carcass ply so that the back surface is in contact with the carcass ply, and a green tire is obtained.
A step in which the green tire is pressurized and heated in a mold ,
The discharge port includes a large number of the grooves,
These grooves are lined up in the width direction,
The pitch of these grooves is 2.5 mm or more and 3.5 mm or less,
The cross-sectional shape of the groove is a semicircle,
The radius of this circle is 0.55 mm or more and 0.65 mm or less,
The number of the grooves is 18 or more and 21 or less,
The cross-sectional shape of the rubber sheet, Ru rectangular der pneumatic tire manufacturing method. A rubber sheet for a sidewall having a protrusion extending in the extrusion direction is formed on the back surface thereof using a die having a groove at the discharge port, and the rubber so that the back surface is in contact with the carcass ply. a step of the green tire is obtained sheet is stuck to the carcass ply, the green tire includes a step to be pressurized and heated in the mold, the discharge port is provided with a plurality of the groove These grooves are arranged in the width direction, the pitch of these grooves is 2.5 mm or more and 3.5 mm or less, the sectional shape of the groove is a semicircle, and the radius of this circle is 0.55 mm or more and 0 and a .65mm or less, or less number 18 or more 21 pieces of the grooves, the pneumatic tire cross-sectional shape of the rubber sheet is obtained by the production method of the pneumatic tire Ru rectangular der.

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