JP6784604B2 - Pneumatic tire manufacturing method and pneumatic tire - Google Patents

Description

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

Conventionally, as a method for manufacturing a pneumatic tire, a ribbon-shaped strip rubber is spirally wound around a drum to form an annular rubber material (for example, Patent Document 1 or Patent Document). 2).

In Patent Document 1 and Patent Document 2, a ribbon winding method is adopted when forming a tread portion of a pneumatic tire. Further, the shape of the conductive rubber covering the rubber ribbon has been devised in order to ensure good energization performance of the pneumatic tire with respect to the rubber ribbon used in the ribbon winding method.

Japanese Unexamined Patent Publication No. 2014-43138 Japanese Unexamined Patent Publication No. 2013-111788

However, when the ribbon construction method disclosed in Patent Document 1 or Patent Document 2 is applied to the sidewall portion, the end portion of the ribbon-shaped strip rubber (rubber ribbon) is exposed on the outer surface of the tire at the sidewall portion of the tire. Cracks may occur starting from the exposed end. In particular, in the case of a pneumatic tire having a flat cross-sectional shape whose thickness is smaller than the tire width, stress tends to concentrate in the vicinity of the maximum tire width of the sidewall portion, so that such cracks may occur remarkably.

An object of the present invention is to provide a pneumatic tire in which cracks in a sidewall portion are suppressed, and a method for manufacturing such a pneumatic tire.

The method for manufacturing a pneumatic tire of the present invention
A ribbon-shaped strip rubber having a coating material coated on at least one acute-angled portion of the core material having a flat cross-sectional shape having a thickness smaller than the width is prepared.
This includes forming a sidewall portion by spirally winding the strip rubber while partially overlapping the strip rubber.
The covering material is located on the outer surface side in the overlapping portion of the strip rubber.
The predetermined elongation tensile stress S300 value specified in JIS-K6251 of the coating material is 0.70 times or more and 0.90 times or less the same value of the core material.

According to this method, the sidewall portion is formed by using the strip rubber in which the acute-angled portion of the core material is covered with the coating material. At this time, since the strip rubber is wound so that the covering material is located on the outer surface side in the overlapping portion of the strip rubber, the end portion (acute angle portion) of the core material which is the starting point of the crack is not exposed on the outer surface of the tire. It is covered with a covering material. Cracks can be suppressed by using a coating material having a property of being resistant to cracks. Further, in the state where the strip rubber is wound, the coating material improves the adhesion between the strip rubbers, so that cracks can be further suppressed. Further, since the material of the covering material has a similar relationship with the material of the core material as described above, the tire performance such as the rigidity of the sidewall portion does not easily change even if the covering material is coated on the core material, that is, the tire performance. Can be suppressed. Furthermore, since the relationship between the core material and the coating material is defined as described above, it is possible to ensure sticking stability and suppress cracks. Specifically, if the above ratio of the S300 value is smaller than 0.70 times, it is resistant to cracks, but the ribbon shape is not stable, that is, it affects the dimensional stability, which makes it difficult to attach. Further, if the above ratio of the S300 value is larger than 0.90 times, the difference in rigidity between the two materials disappears and the material becomes vulnerable to cracks, so that it becomes difficult to suppress the cracks. Therefore, the range of the above ratio of the S300 value is the appropriate range.

The width of the strip rubber may be 30% or less of the tire height.

According to this method, since the width of the strip rubber is defined as described above, the shape of the sidewall portion can be appropriately formed according to the tire height. If the width of the strip rubber exceeds the above-mentioned specified value, it is difficult to accurately form the fine shape of the sidewall portion, especially in a tire having a low tire height. Here, the width of the strip rubber means the width of the sticking surface at the time of winding.

In the strip rubber, the covering material may cover only at least one acute-angled portion of the core material.

According to this method, since the covering material covers only the acute-angled portion instead of the entire circumference of the core material, the physical property value of the strip rubber as a whole does not change significantly. Therefore, even if the coating material is coated on the core material, the tire performance does not change significantly, that is, the deterioration of the tire performance can be suppressed.

The covering material may cover only one acute-angled portion of the core material.

According to this method, the amount of coating can be reduced by coating the covering material in one place, so that even if the covering material is coated on the core material, the tire performance such as the rigidity of the sidewall portion can be deteriorated. The property can be reduced. Further, since the strip rubber is usually partially overlapped and wound, only one end of the strip rubber is exposed to the outer surface. Therefore, by covering only the exposed end of the strip rubber with the coating material, the crack suppressing effect can be obtained as described above.

The covering material covers two acute-angled portions of the core material.
The covering range of the covering material may be a range that is 5% or more of the bottom side length of the core material and does not overlap with the covering material of the adjacent strip rubber at the bottom portion of the core material.

According to this method, since the strip rubber in a state where the two acute-angled portions of the core material are covered with the coating material is wound, the adhesion at both ends of the strip rubber is improved and cracks can be suppressed. Further, when the covering range of the covering material is 5% or more of the bottom length of the core material, the crack suppressing effect can be exhibited. Further, since the covering range does not overlap with the covering material of the adjacent strip rubber, it is possible to suppress the deterioration of the tire performance due to the interference between the covering materials.

The pneumatic tire of the present invention
A ribbon-shaped strip rubber in which at least one acute-angled portion of a core material having a flat cross-sectional shape, which is smaller in thickness than the width, is coated with a coating material is provided in the sidewall portion.
The strip rubber is partially overlapped and spirally wound.
The covering material is located on the outer surface side in the overlapping portion of the strip rubber.
The predetermined elongation tensile stress S300 value specified in JIS-K6251 of the coating material is 0.70 times or more and 0.90 times or less the same value of the core material.

According to this configuration, in a pneumatic tire, cracks in the sidewall portion can be suppressed as described above.

According to the present invention, in the pneumatic tire and the manufacturing method thereof, since the sidewall portion is formed by using the strip rubber in which the acute angle portion of the core material is covered with the coating material, cracks in the sidewall portion are suppressed. it can.

Schematic half-cross-sectional view of a pneumatic tire manufactured by the method for manufacturing a pneumatic tire according to an embodiment of the present invention. The schematic side view which shows the wound state of the strip rubber of the sidewall part. Schematic cross-sectional view of the strip rubber along lines III-III of FIG. A schematic cross-sectional view showing a wound state of strip rubber. FIG. 3 is a schematic cross-sectional view showing a modified example of the strip rubber of FIG. Schematic half-cross section of the meridian of the pneumatic tire formed by the strip rubber of FIG.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows a schematic meridian half-section view of a pneumatic tire AT manufactured by the manufacturing method according to the present embodiment. In addition, in order to clarify the illustration, the hatching indicating the cross section is omitted. The pneumatic tire AT is provided with a carcass ply 2, a belt layer 3, and a reinforcing layer 4 from the inner liner 1 located on the inner diameter side in the tire radial direction toward the tire outer diameter side. Both ends of the carcass ply 2 extend to the bead core 5, and the carcass ply 2 is folded back from the inside to the outside of the tire so as to sandwich the bead filler 6. Further, the pneumatic tire AT is composed of a tread portion 7, a shoulder portion 8, a sidewall portion 9, and a bead portion 10 on the surface.

In the tread portion 7 and the shoulder portion 8, the belt layer 3 is composed of a first belt portion 12 arranged inside in the tire radial direction and a second belt portion 13 arranged outside. The first belt portion 12 extends halfway through the shoulder portion 8 in the tire width direction. The shoulder portion 8 is formed with a shoulder lateral groove 14 extending in the tire width direction. The second belt portion 13 is located inside the first belt portion 12 in the tire width direction.

The reinforcing layer 4 is formed by arranging fiber cords of a resin material (for example, nylon 66) in a plurality of rows at predetermined intervals and coating them with a rubber material. The reinforcing layer 4 is spirally wound so as to cover the belt layer 3.

The sidewall portion 9 is formed by spirally winding a sidewall rubber having a predetermined shape and material, which will be described later, as a strip rubber 11 from the side surface of the shoulder portion 8.

The pneumatic tire AT having the above configuration is obtained by vulcanizing the green tire GT formed by the ribbon method. That is, the green tire GT indicates a raw tire before vulcanization molding, and the pneumatic tire AT indicates a tire as a product after vulcanization molding. Here, since the tread portion 7, the shoulder portion 8, and the bead portion 10 are formed by a normal ribbon construction method, description thereof will be omitted. Hereinafter, the process of forming the sidewall portion 9 will be described in detail.

FIG. 2 is a schematic side view showing a wound state of the strip rubber 11 of the sidewall portion 9. The winding device 15 includes a drum 16 that is rotationally driven, an extruder 17 that supplies the strip rubber 11 to the drum 16, and a crimping roller 19 that presses the strip rubber 11 against the drum 16.

FIG. 3 is a cross-sectional view of the strip rubber 11 along the line III-III of FIG. The strip rubber 11 is composed of a core material 11a and a covering material 11b, both of which extend in a ribbon shape. The cross section of the core material 11a of the present embodiment has a flat shape having a thickness T smaller than the length L of the bottom portion 11d, and is an isosceles triangle shape having two acute-angled portions 11c (see FIG. 3). The covering material 11b covers the two acute-angled portions 11c of the core material 11a. In other words, the entire circumference of the core material 11a is not covered, and only the two acute-angled portions 11c are covered with the covering material 11b.

In the present embodiment, in the bottom side portion 11d of the strip rubber 11 (the side portion forming the lower sticking surface in the drawing), the covering range of the covering material 11b is about 20% of the length L of the bottom side portion 11d of the core material 11a. Is. That is, the total D (= d1 + d2) of the respective lengths d1 and d2 of the covering material 11b in the bottom portion 11d is about 20% (D / L = 0.2) of the length L of the bottom portion 11d of the core material 11a. is there. At this time, preferably, the covering range of the covering material 11b is 5% or more of the length L of the bottom side portion 11d of the core material 11a in the bottom side portion 11d of the strip rubber 11 (D / L ≧ 0.05). Further, the thickness T of the cross-sectional shape of the strip rubber 11 is smaller than the width W, and the cross-sectional shape of the strip rubber 11 is flat. For example, the thickness T of the cross-sectional shape of the strip rubber 11 of the present embodiment is about 2 mm, and the width W is about 30 mm. In particular, the width W is preferably 30% or less of the tire height H (see FIG. 1). Here, the width W of the strip rubber means the width of the sticking surface at the time of winding.

As shown in FIG. 4, the covering range of the covering material 11b is preferably a range that does not overlap with the covering material 11b of the adjacent strip rubber 11 when wound. That is, it is preferable that a gap S exists between the covering materials 11b of the adjacent strip rubber 11. Further, the core material 11a and the covering material 11b are similar materials. Specifically, it is preferable that the predetermined elongation tensile stress S300 value specified in JIS-K6251 of the covering material 11b is 0.70 times or more and 0.90 times or less the same value of the core material 11a. For example, this ratio of this embodiment is 0.80 times.

Returning to FIG. 2, the drum 16 has a substantially columnar shape, and is rotationally driven so that the sticking speed of the strip rubber 11 on the surface is, for example, 40 to 100 (m / rpm).

The extruder 17 is configured to extrude the heated strip rubber 11 through the base 18. Here, the heating temperature is set to a value of 120 ° C. or lower in which the strip rubber 11 is vulcanized and the physical properties do not change. The extrusion port of the base 18 is formed in a triangular shape in accordance with the cross-sectional shape (triangular shape shown in FIG. 3) of the strip rubber 11.

The crimping roller 19 is rotatably attached to a tip portion of a rod 21 that expands and contracts from the cylinder 20. Therefore, the crimping roller 19 is brought into contact with and separated from the drum 16 or the green tire GT, and the strip rubber 11 is wound and crimped at the same time.

The winding device 15 itself can reciprocate with respect to the drum 16 along its rotation axis. Here, the moving speed of the winding device 15 is set so that the feed pitch of the strip rubber 11 wound around the drum 16 is, for example, about 50% of the width dimension W (see FIG. 3).

The method of winding the strip rubber 11 of the sidewall portion 9 by the winding device 15 having the above configuration is as follows.

First, the strip rubber 11 is extruded from the extruder 17 through the base 18 in a state where the green tire GT having a part already formed such as the inner liner 1 and the carcass ply 2 is fixed to the drum 16. When extruded through the mouthpiece 18, the covering material 11b covers the acute-angled portion 11c of the core material 11a as described above (see FIG. 3). At this time, the strip rubber 11 is heated in the extruder 17 to be softened. However, in the present embodiment, since the thickness is about 2 mm, heating is not always required, and even when heated, heat shrinkage after cooling can be suppressed.

Subsequently, the drum 16 is rotated, and the strip rubber 11 is pressed against the green tire GT by the crimping roller 19. The winding device 15 moves along the drum 16 at a constant speed. The strip rubber 11 is spirally wound around the drum 16 while being partially overlapped and fed at a feed pitch (half pitch) of about half the width dimension in detail. At this time, the covering material 11b is wound so as to be located on the outer surface side of the tire at the overlapping portion of the strip rubber 11. However, when both of the two acute-angled portions 11c are covered with the covering material 11b as in the present embodiment, the covering material 11b of one acute-angled portion 11c is inevitably located on the outer surface side of the tire. Become. By winding the strip rubber 11 in this way, the sidewall portion 9 is formed.

The pneumatic tire AT shown in FIG. 1 is completed by vulcanizing the green tire GT having the sidewall portion 9 formed as described above at, for example, at 160 ° C. for about 30 minutes. Such a pneumatic tire AT has the following effects.

According to the present embodiment, the sidewall portion 9 is formed by using the strip rubber 11 in a state where the acute-angled portion 11c of the core material 11a is covered with the coating material 11b. At this time, since the strip rubber 11 is wound so that the covering material 11b is located on the outer surface side in the overlapping portion of the strip rubber 11, the end portion (acute angle portion 11c) of the core material 11a which is the starting point of the crack is the outer surface of the tire. It is not exposed to the surface and is covered with the covering material 11b. Cracks can be suppressed by using a coating material 11b having a property of being resistant to cracks. Further, in the state where the strip rubber 11 is wound, the coating material 11b improves the adhesion between the strip rubbers 11, so that cracks can be further suppressed. Further, since the material of the covering material 11b has a similar relationship with the material of the core material 11a as described above, even if the covering material 11b is covered with the core material 11a, the tire performance such as the rigidity of the sidewall portion 9 changes. It is difficult, that is, the deterioration of tire performance can be suppressed. Furthermore, since the relationship between the materials of the core material 11a and the covering material 11b is defined as described above, it is possible to ensure sticking stability and suppress cracks. Specifically, if the above-mentioned ratio of the S300 value is smaller than 0.70 times, it is resistant to cracks, but the ribbon shape of the strip rubber 11 is not stable, that is, it affects the dimensional stability. It will be difficult. Further, if the above-mentioned ratio of the S300 value is larger than 0.90 times, the difference in rigidity between the two materials disappears and the material becomes vulnerable to cracks, so that it becomes difficult to suppress cracks. Therefore, the appropriate range of the ratio of the S300 value is 0.70 times or more and 0.90 times or less.

Further, since the width W (see FIG. 3) of the strip rubber 11 is defined within a preferable range as described above, the shape of the sidewall portion 9 is appropriately formed according to the tire height H (see FIG. 1). it can. If the width W of the strip rubber exceeds the above-mentioned specified value (30%), it is difficult to accurately form the fine shape of the sidewall portion 9, especially in a tire having a low tire height H.

Further, since the covering material 11b covers only the acute-angled portion 11c instead of the entire circumference of the core material 11a, the physical property value of the strip rubber 11 as a whole does not change significantly. Therefore, even if the coating material 11b is coated on the core material 11a, the tire performance does not change significantly, that is, the deterioration of the tire performance can be suppressed.

Further, since the strip rubber 11 in a state where the two acute-angled portions 11c of the core material 11a are covered with the coating material 11b is wound, the adhesion at both ends of the strip rubber 11 is improved and cracks can be suppressed. Further, when the covering range of the covering material 11b is 5% or more of the bottom length L of the core material, the crack suppressing effect can be exhibited. Further, since the covering range does not overlap with the covering material 11b of the adjacent strip rubber 11, it is possible to suppress the deterioration of the tire performance due to the interference between the covering materials 11b.

As described above, in the pneumatic tire AT manufactured by the manufacturing method of the present embodiment, cracks in the sidewall portion 9 can be suppressed as described above.

FIG. 5 is a schematic cross-sectional view showing a modified example of the strip rubber 11 of FIG. As a modification of the present embodiment, the coating material 11b of the strip rubber 11 constituting the sidewall portion 9 covers only one acute-angled portion 11c of the core material 11a. FIG. 6 shows a pneumatic tire AT in which the sidewall portion 9 is formed by such a strip rubber 11. In this modification, the strip rubber 11 is wound so that the covering material 11b is located on the outer surface side at the overlapping portion of the strip rubber 11.

According to this deformation, since the coating amount can be reduced by covering the covering material 11b at one place, the tire performance of the sidewall portion 9 deteriorates even if the covering material 11b is covered with the core material 11a. The possibility can be reduced. Further, since the strip rubber 11 is usually wound by partially overlapping the strip rubber 11, only one end of the strip rubber 11 (the acute-angled portion 11c of the core material 11a) is exposed to the outer surface. Therefore, by covering only the exposed end of the strip rubber 11 with the coating material 11b, the crack suppressing effect can be obtained as described above.

In the present embodiment, the cross-sectional shape of the strip rubber 11 is triangular, but the cross-sectional shape of the strip rubber 11 is not limited to this, and may have an acute-angled portion, for example, a trapezoidal shape or a semi-circular shape (generally half). It can be circular) and so on. However, if the cross-sectional shape of the strip rubber 11 is triangular, it is easy to form an arbitrary shape, so that the strip rubber 11 is preferably triangular.

AT ... Pneumatic tire GT ... Green tire 1 ... Inner liner 2 ... Carcass ply 3 ... Belt layer 4 ... Reinforcement layer 5 ... Bead core 6 ... Bead filler 7 ... Tread part 8 ... Shoulder part 9 ... Sidewall part 10 ... Bead part 11 ... Strip rubber 11a ... Core material 11b ... Coating material 11c ... Sharp corner part 11d ... Bottom part 12 ... First belt part 13 ... Second belt part 14 ... Shoulder lateral groove 15 ... Winding device 16 ... Drum 17 ... Extruder 18 ... Base 19 ... Crimping roller 20 ... Cylinder 21 ... Rod

Claims (6)

A ribbon-shaped strip rubber having a coating material coated on at least one acute-angled portion of the core material having a flat cross-sectional shape having a thickness smaller than the width is prepared.
A method for manufacturing a pneumatic tire, which comprises spirally winding the strip rubber while partially overlapping the strip rubber to form a sidewall portion.
The covering material is located on the outer surface side in the overlapping portion of the strip rubber.
A method for manufacturing a pneumatic tire, wherein the predetermined elongation tensile stress S300 value specified in JIS-K6251 of the covering material is 0.70 times or more and 0.90 times or less the same value of the core material. The method for manufacturing a pneumatic tire according to claim 1, wherein the width of the strip rubber is 30% or less of the tire height. The method for manufacturing a pneumatic tire according to claim 1 or 2, wherein in the strip rubber, the covering material covers only at least one acute-angled portion of the core material. The method for manufacturing a pneumatic tire according to any one of claims 1 to 3, wherein the covering material covers only one acute-angled portion of the core material. The covering material covers two acute-angled portions of the core material.
Claims 1 to 3 claim that the covering range of the covering material is a range that is 5% or more of the bottom side length of the core material and does not overlap with the covering material of the adjacent strip rubber at the bottom portion of the core material. The method for manufacturing a pneumatic tire according to any one of the above. A ribbon-shaped strip rubber in which at least one acute-angled portion of a core material having a flat cross-sectional shape, which is smaller in thickness than the width, is coated with a coating material is provided in the sidewall portion.
The strip rubber is partially overlapped and spirally wound.
The covering material is located on the outer surface side in the overlapping portion of the strip rubber.
A pneumatic tire in which the predetermined elongation tensile stress S300 value specified in JIS-K6251 of the coating material is 0.70 times or more and 0.90 times or less the same value of the core material.

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