JP2016141005A - Tire manufacturing method and mold used therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a failure such as black remaining.SOLUTION: The tire manufacturing method is provided for manufacturing a tire which includes a carcass stretching from a tread part through the side wall parts of both sides to a bead part and in which a projected pattern raised from a virtual contour surface along the outer surface of the carcass is formed in the side wall part, the projected part having a first color tone rubber layer and a second color tone rubber layer stacked together, and a part of the second color tone rubber layer is exposed in the state of being surrounded with the first color tone rubber layer. The method includes the step of forming a rubber sheet including a second color tone rubber layer and a first color tone rubber layer covering the second color tone rubber layer and having a projected part on the surface, the step of molding a green tire having a rubber sheet disposed outside the carcass of the side wall part, the step of heating and pressurizing the green tire in a mold having a shape corresponding to the projected pattern, and the step of scraping the first color tone rubber layer to expose at least a part of the second color tone rubber layer.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a tire manufacturing method and a mold used for the tire manufacturing method.

  Conventionally, a pneumatic tire has been proposed in which a convex pattern (raised letter) in which a character indicating a mark or a tire size is raised is formed on the sidewall portion.

  In addition, a pneumatic tire has been proposed in which a non-black rubber such as white is arranged on the raised surface of the convex pattern, thereby improving the contrast of the convex pattern and improving the appearance of the sidewall portion. .

  Such a pneumatic tire is manufactured as follows, for example. That is, a green tire (raw tire) in which a white rubber layer made of non-black rubber (for example, white rubber) and a cover rubber layer covering the white rubber layer is arranged on the sidewall portion is molded. The green tire is vulcanized by heating and pressurizing in a mold with a vulcanizer to form a convex pattern. It is manufactured by causing a non-black rubber layer (for example, a white rubber layer) to appear by scraping the cover rubber layer covering the raised surface of the convex pattern.

  Further, for example, Patent Document 1 describes a technique in which a non-black rubber such as white is arranged on a raised surface of a convex pattern by winding a rubber ribbon.

JP 2005-212197 A

  However, in such a tire manufacturing method, when the thickness of the cover rubber layer made of black rubber is increased, the cover rubber layer is not completely scraped and the black rubber remains on the raised surface, so-called black residue failure occurs. It has become.

  This invention is made | formed in view of the above, Comprising: It aims at providing the metal mold | die used for the tire manufacturing method and tire manufacturing method which can prevent defects, such as a black residue.

  In order to solve the above-described problems and achieve the object, a tire manufacturing method according to an aspect of the present invention includes a carcass extending from a tread portion to a bead portion through sidewalls on both sides, and the carcass is provided in the sidewall portion. A convex pattern raised from a virtual contour surface along the outer surface of the first pattern is formed, and the convex pattern is formed by laminating a rubber layer of a first color and a rubber layer of a second color different from the first color, A tire manufacturing method for manufacturing a pneumatic tire in which a part of the rubber layer of the second color is exposed in a state surrounded by the rubber layer of the first color, the rubber layer of the second color And forming a rubber sheet that covers the rubber layer of the second color and includes the rubber layer of the first color having a convex portion on the surface, and outside the carcass of the sidewall portion, Rubber sheet was placed Forming a lean tire; heating and pressurizing the green tire in a mold having a shape corresponding to the convex pattern; and scraping the rubber layer of the first color to form the second color. Exposing at least a portion of the rubber layer.

  The convex pattern is preferably composed of characters, symbols or figures.

  In the step of forming the rubber sheet, it is preferable to form the convex portion on the rubber sheet using a base having a groove at the discharge port.

  It is preferable that the discharge port includes a plurality of the grooves, the plurality of grooves are arranged in the tire width direction, and the convex portion having a shape corresponding to the plurality of the grooves is formed on the rubber sheet.

  The cross-sectional shape of the groove is a semicircle, and the radius of the semicircle is preferably 0.3 mm or more and 0.5 mm or less.

  It is preferable that the mold has a concave portion deeper than the height of the convex portion at a position corresponding to the convex portion.

  It is preferable that the concave portion is provided at least at a position corresponding to the entire circumference of the edge portion of the convex pattern.

  The recess preferably has a depth from the surface of the mold corresponding to a main molding surface other than the convex pattern of 3.0 mm or more and 5.5 mm or less.

  It is preferable to further include a vent hole provided in the concave portion for discharging air between the mold and the green tire.

It is preferable that one vent hole is provided in the deepest portion of the recess per 80 mm ² area.

  The vent hole is preferably provided at least in the recess.

  The metal mold | die by an aspect with this invention is a metal mold | die used for said tire manufacturing method.

  According to the present invention, a rubber sheet that covers the second color rubber layer and includes the first color rubber layer having a convex portion on the surface is formed, and the rubber sheet is disposed outside the carcass of the sidewall portion. By molding the green tire, it is possible to prevent defects such as black residue when the rubber layer of the first color is shaved to expose at least a part of the rubber layer of the second color.

FIG. 1 is a sectional view in the tire meridian direction showing a pneumatic tire obtained by a tire manufacturing method according to an embodiment of the present invention. FIG. 2 is an enlarged view showing a sidewall portion of the pneumatic tire shown in FIG. Drawing 3 is a figure showing a process of a manufacturing method of a pneumatic tire. FIG. 4 is an enlarged view showing an example of the sidewall portion before performing the vulcanization step. FIG. 5 is an enlarged view showing an example of the sidewall portion after performing the vulcanization step. FIG. 6A is a cross-sectional view showing an example of a rubber sheet constituting the cover layer of the sidewall portion. FIG. 6B is a perspective view showing an example of a rubber sheet constituting the cover layer of the sidewall portion. FIG. 7A is a cross-sectional view showing an example of the structure of the die of the extrusion device. FIG. 7B is an enlarged view of a part of the die of the extrusion device. FIG. 8A is a diagram illustrating an example of a mold used in a process of heating and pressurizing a green tire. FIG. 8B is a diagram showing another example of a mold used in a vulcanization process for heating and pressurizing a green tire. FIG. 8C is a diagram illustrating an example of a mold having a vent hole. FIG. 8D is a diagram illustrating an example of a mold having a vent hole. FIG. 9 is a diagram illustrating an example of the sidewall portion after the vulcanization process in the tire of the comparative example. FIG. 10A is a diagram illustrating an example of a sidewall portion after polishing in the tire of the comparative example. FIG. 10B is a partially enlarged view of FIG. 10A. 10C is a partial cross-sectional view of FIG. 10B. FIG. 10D is a partially enlarged view of FIG. 10A.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings, but the present invention is not limited thereto. The components of the embodiments described below can be combined as appropriate. Some components may not be used.

(Pneumatic tire)
A pneumatic tire obtained by the tire manufacturing method according to the embodiment of the present invention will be described. FIG. 1 is a sectional view in the tire meridian direction showing a pneumatic tire obtained by a tire manufacturing method according to an embodiment of the present invention. FIG. 2 is an enlarged view showing a sidewall portion of the pneumatic tire shown in FIG.

  As shown in FIG. 1, the pneumatic tire 1 includes a bead core 2, a bead filler 3, a carcass layer 4, a belt layer 5, a tread portion 6, and a sidewall portion 7. The bead core 2 has an annular structure and is configured as a pair of left and right. The bead filler 3 is disposed on the outer periphery of the bead core 2 in the tire radial direction and reinforces the bead portion of the tire. The carcass layer 4 has one or a plurality of stacked carcass plies 40 and is bridged in a toroidal shape between the left and right bead cores 2 and 2 to form a tire skeleton.

  In addition, the carcass layer 4 reaches the bead portion through the sidewall portion 7. Both end portions of the carcass layer 4 are wound up so as to sandwich the bead filler 3, and are folded and locked outward in the tire width direction. The belt layer 5 includes a plurality of stacked belt plies 51 and 52, and is disposed on the outer periphery in the tire radial direction of the carcass layer 4. The tread portion 6 is formed by a tread rubber disposed on the outer circumference in the tire radial direction of the carcass layer 4 and the belt layer 5. The sidewall portion 7 has a sidewall rubber disposed outside the bead filler 3 and the carcass layer 4 in the tire width direction.

  Moreover, as shown in FIG. 1, centering on the equator plane CL, the left and right sidewall portions 7 are, for example, one of white sidewalls and the other of normal (black) sidewalls. The sidewall portion 7 on the white sidewall side includes black rubber layers 71U and 71L and a white rubber layer 72. For this reason, on the white sidewall side, a black portion and a white portion appear on the surface.

  A convex pattern is formed on the sidewall portion 7. The convex pattern is formed by stacking the black rubber layers 71U and 71L and the white rubber layer 72, and exposing a part of the white rubber layer 72 surrounded by the black rubber layers 71U and 71L. . The convex pattern is raised from a virtual contour surface 75 along the outer surface of the carcass layer 4. The convex pattern is, for example, a character, a symbol, or a figure. However, the convex pattern is not limited to these.

  Further, the black rubber layers 71U and 71L are made of, for example, a diene rubber material reinforced with carbon. The white rubber layer 72 is made of, for example, a diene rubber material in which a white filler is reinforced with titanium dioxide and clay. For this reason, the rigidity of the white rubber layer 72 is smaller than the rigidity of the black rubber layers 71U and 71L. On the other hand, the other side wall (side different from the white side wall side) is composed of only the black rubber layer 71. The hatched portion shown in FIGS. 1 and 2 indicates that the portion is a white rubber layer. The same applies to other drawings referred to in the following description.

  As shown in FIG. 1, belt reinforcing layers 8 and 8 for reinforcing the belt layer 5 are disposed at both ends (both ends in the tire width direction) of the belt layer 5, respectively. These belt reinforcing layers 8 are formed of a belt-shaped belt cover material. The belt cover material is configured by arranging a plurality of fiber materials made of, for example, 6-6 nylon. The belt reinforcing layer 8 is disposed around the end of the belt layer 5 so as to be wound around the tire radial direction from the outer side in the tire radial direction.

  As shown in FIGS. 1 and 2, the tire 1 includes black rubber layers 71U and 71L, a white rubber layer 72, a cover layer 73, and an undercover layer 74. The under cover layer 74 is provided on the tire inner diameter side of the white rubber layer 72. The cover layer 73 covers a part of the white rubber layer 72. The under cover layer 74 is made of, for example, black rubber.

  In this example, the white rubber layer 72 is bonded to the under cover layer 74. The black rubber layers 71U and 71L are bonded to the white rubber layer 72 and the under cover layer 74. The cover layer 73 is adhered to the black rubber layers 71U and 71L and the white rubber layer 72.

  The white rubber layer 72 has a flat surface 720 exposed as a sidewall. The flat surface 720 is exposed as a sidewall when the black rubber layer covering the surface of the white rubber layer 72 is removed by polishing.

  That is, FIG. 2 shows the sidewall portion 7 after polishing. The flat surface 720 of the white rubber layer 72 forms a convex pattern (character, symbol or figure). The convex pattern includes characters, symbols or figures. The characters and symbols are used for notation relating to the size of the tire 1, for example. A figure adds a design to the sidewall of the tire 1, for example.

  The portions other than the portion where the convex pattern of the white rubber layer 72 is exposed are covered with the black rubber layers 71U and 71L. For this reason, a convex pattern can express a character, a symbol, or a figure.

(Tire manufacturing method)
Drawing 3 is a figure showing a process of a manufacturing method of a pneumatic tire mentioned above. As shown in FIG. 3, the tire manufacturing method includes the following steps.

  In step S101, sidewall rubber is obtained by extrusion molding. In step S102, members such as a cap and a belt are supplied.

  Step S103 is a molding process. In step S103, members such as sidewall rubber, caps, and belts are assembled to form a green tire.

  Step S104 is a vulcanization process. In step S104, the green tire is vulcanized by being heated and pressurized in a mold by a vulcanizer.

  FIG. 4 is an enlarged view showing an example of the sidewall portion 7 before performing the vulcanization step. A broken line 200H in FIG. 4 shows a partial shape of the mold. This mold is used when a vulcanization process is performed on a green tire. The vulcanization step is a step of heating and pressurizing the green tire from the inside toward the mold.

  As shown in FIG. 4, the concave portion B is provided at a position corresponding to the convex portion T of the cover layer 73 of the rubber sheet 70. The corresponding position is a position where the portion having the convex portion T of the rubber sheet 70 enters the concave portion B of the mold in the vulcanization process, and the convex portion T of the rubber sheet 70 and the concave portion B of the mold are in a one-to-one relationship. There is no need to support it. By providing the concave portion B at a position corresponding to the convex portion T of the cover layer 73 of the rubber sheet 70, the raw rubber can be flowed well in the vulcanization process.

  FIG. 5 is an enlarged view showing an example of the sidewall portion 7 after performing the vulcanization step. As shown in FIG. 5, the side wall part 7 after performing a vulcanization | cure process has the convex part T corresponding to the recessed part provided in the metal mold | die.

  Next, the sidewall portion 7 after the vulcanization process is polished. By the polishing process, the black rubber layer covering the surface of the white rubber layer 72 is shaved and removed. The polishing process is performed up to the broken line 7H shown in FIG. The black rubber layer is removed by polishing to the portion of the broken line 7H, and a flat surface 720 appears on the sidewall portion 7 after the polishing as shown in FIG.

  Step S105 is a polishing process. In step S105, the sidewall portion after the vulcanization process is polished. The polishing process is, for example, buffing, that is, buffing. By polishing the sidewall portion, a part of the black rubber layer covering the surface of the white rubber layer is removed. For this reason, the white rubber layer is exposed on the sidewall as a convex pattern such as letters.

  Step S106 is an inspection process. In step S106, an appearance inspection is performed on the tire after polishing.

(Green tire)
The green tire is a tire that is formed by assembling and molding members such as a sidewall rubber, a cap, and a belt before the vulcanization process. Green tires are also called raw tires. The manufacturing method of the present embodiment uses the rubber sheet 70 in the molding step (step S103).

(Rubber sheet)
FIG. 6A is a cross-sectional view showing an example of a rubber sheet 70 constituting the cover layer 73 of the sidewall portion. FIG. 6B is a perspective view showing an example of the rubber sheet 70 constituting the cover layer 73 of the sidewall portion. As shown in FIGS. 6A and 6B, the rubber sheet 70 includes black rubber layers 71U and 71L, a white rubber layer 72, and a cover layer 73.

  The black rubber layer 71U is a black rubber layer above the white rubber layer 72 (outer in the tire radial direction) in the sidewall rubber.

  The black rubber layer 71 </ b> L is a black rubber layer below (in the tire radial direction) the white rubber layer 72 in the sidewall rubber.

  The white rubber layer 72 is exposed when the cover layer 73 is removed by polishing, and forms a convex pattern (characters, symbols, or figures).

  The cover layer 73 covers a part of the surface of the white rubber layer 72. The cover layer 73 has a plurality of convex portions T. Each convex portion T has a shape that is continuous in parallel with the end portion 711. The cover layer 73 can be obtained by extrusion molding using a die having a groove at the discharge port. The cover layer 73 is attached to the surface of the white rubber layer 72 so as to cover the white rubber layer 72.

  In addition, the convex part T is not limited to the shape which continues in parallel with the edge part 711. FIG. For example, the convex part T may have a lattice shape.

(Base)
The cover layer 73 can be obtained, for example, by extruding black rubber using an extrusion molding apparatus. The cover layer 73 can be obtained by providing a groove in the die of the extrusion molding device.

  FIG. 7A is a cross-sectional view showing an example of the structure of the die of the extrusion device. As shown in FIG. 7A, the base 10 has a plurality of grooves M. The plurality of grooves M are continuous from the back side to the near side in the drawing. The plurality of grooves M are arranged so as to be parallel to the tire width direction when the cover layer 73 is provided on the tire 1. In FIG. 7A, the rubber material is extruded from the back surface side to the near side in the drawing. Thereby, convex portions T having a shape corresponding to the plurality of grooves M are formed on the cover layer 73. The interval D between the grooves M is, for example, not less than 2.5 mm and not more than 3.5 mm.

  By arranging a plurality of protrusions on the cover layer 73 in the tire width direction, the flow of air can be smoothly flowed by the gap between the recess B and the cover layer 73 in the heating and pressurizing step, and the raw rubber can flow well. . As a result, the distance between the convex shapes constituting the convex pattern, that is, the character, symbol, or figure can be appropriately maintained.

  FIG. 7B is an enlarged view of a part of the base of FIG. 7A. As shown in FIG. 7B, the base 10 has a groove M at the discharge port. The cross-sectional shape of the groove M is a semicircle in this example. By having a curved surface portion such as a semicircle, the rubber in the vulcanization process can be made to flow better than a shape having a corner portion.

  The radius R of the semicircle is not less than 0.3 mm and not more than 0.5 mm, for example. If the radius is less than 0.3 mm, it may be difficult to maintain the shape after processing and extrusion. Further, if the radius exceeds 0.5 mm, the cover layer 73 may become thick.

(Mold)
FIG. 8A is a diagram illustrating an example of a mold used in a process of heating and pressurizing a green tire (raw tire). As shown in FIG. 8A, the mold 200A has a recess 201 corresponding to a character, symbol, or figure. The mold 200 </ b> A has a recess B that is deeper than the bottom surface 201 </ b> A of the recess 201. A plurality of recesses B are provided in the recess 201.

  As already described with reference to FIGS. 1 and 2, the plurality of recesses B are provided at positions corresponding to the protrusions T of the cover layer 73. Each concave portion B is deeper than the height of the convex portion T.

  Since the concave portion B has a shape corresponding to the convex portion T, the black rubber layer is sufficiently stretched on the surface of the mold corresponding to the convex pattern in the vulcanization process of heating and pressurizing the green tire. For this reason, the black rubber layer is disposed in an appropriate amount. Therefore, the black residue after polishing can be eliminated without increasing the amount of white rubber. In other words, a measure to increase the amount of white rubber can be considered in order to improve the black residue, but this measure has a problem that the cost increases. According to this embodiment, such a problem can be avoided.

  FIG. 8B is a diagram showing another example of a mold used in a vulcanization process for heating and pressurizing a green tire. As shown in FIG. 8B, the mold 200B has recesses B11, B12, B13, and B14. The recesses B11, B12, B13, B14 are provided at positions corresponding to the entire circumference of the edge portion of the convex pattern. The edge portion of the convex pattern often has a defect such as a black residue after polishing. For this reason, as shown to FIG. 8B, generation | occurrence | production of such a defect can be suppressed by providing a recessed part in the position corresponding to the perimeter of the edge part of a convex pattern at least.

  The mold 200 </ b> B has a recess B deeper than the height of the protrusion T at a position corresponding to the protrusion T. A concave portion B having a shape corresponding to the convex portion T is formed in the concave portion 201 of the mold 200B. Since the convex portion T and the concave portion B are provided, the cover rubber layer is sufficiently stretched on the inner surface of the mold 200B, arranged in an appropriate amount, and the black after polishing without increasing the amount of white rubber. The rest can be eliminated.

  8A and 8B, the recess B has a depth DH from the surface 202 of 3.0 mm to 5.5 mm. The surface 202 is a surface of the mold corresponding to the main molding surface that is a portion other than the convex pattern. If the depth DH from the surface 202 is smaller than 3.0 mm, the volume of the recess 201 becomes small, so that the cover rubber layer cannot be sufficiently stretched, and the cover rubber may be increased in thickness. Conversely, if the depth DH is greater than 5.5 mm, more sidewall rubber may enter the recess 201, causing the carcass cord to meander, and may deteriorate uniformity and steering stability.

(Benthole)
The mold may have a vent hole. The vent hole exhausts air and generated gas remaining between the inner surface of the mold and the green tire to the outside of the mold when the green tire is vulcanized by heating and pressurizing inside the mold with a vulcanizer. It is a vent for.

  8C and 8D are diagrams showing examples of a mold having a vent hole. FIG. 8C shows a configuration of a mold 200C in which a vent hole is provided in the mold 200A of FIG. 8A. FIG. 8D shows a configuration of a mold 200D in which a vent hole is provided in the mold 200B of FIG. 8B.

  As shown in FIG. 8C, the mold 200C has a vent hole BH. The vent hole BH opens, for example, in the deepest part of the recess B. You may provide a vent hole also in parts other than the recessed part B. FIG. In order to perform exhaust efficiently, it is preferable to provide at least the deepest part of the recess B.

  Further, as shown in FIG. 8D, the mold 200D has vent holes BH1, BH2, BH3, and BH4. The vent holes BH1, BH2, BH3, and BH4 open to the deepest portions of the recesses B11, B12, B13, and B14, respectively. The vent hole may be provided in a portion other than the recesses B11, B12, B13, and B14.

  As shown in FIGS. 8C and 8D, it is preferable that a certain number of vent holes BH, BH1, BH2, BH3, and BH4 are arranged in the recesses B, B11, B12, B13, and B14. Thereby, when the green tire is heated and pressurized in the mold, the black rubber layer is sucked up from the inner surface of the mold.

For example, one vent hole is provided in the deepest part of the recesses B, B11, B12, B13, and B14 per 80 mm ² area. If vent holes are provided at this density, the black rubber layer can be appropriately sucked up.

(Defects such as black residue)
In the inspection process, defects such as black residue may be found in the sidewall portion. FIG. 9 is a diagram illustrating an example of the sidewall portion after the vulcanization process in the tire of the comparative example. When the cover layer 73 shown in FIGS. 4 and 6A is not used, the cover layer 73 does not have the convex portion T, or the mold does not have a concave portion deeper than the height of the convex portion T. In this case, the flow of black rubber in the vulcanization process becomes worse. For this reason, as shown in FIG. 9, the thickness of the black rubber layers 71U and 71L is not uniform in the sidewall portion after the vulcanization step.

  FIG. 10A is a diagram illustrating an example of a sidewall portion after a polishing step in a tire of a comparative example. FIG. 10B is an enlarged view of a portion of an ellipse 80A in FIG. 10A. 10C is a cross-sectional view taken along a line AA in FIG. 10B.

  When the cover layer 73 shown in FIG. 4 and FIG. 6A does not have the convex portion T, or when the mold does not have the concave portion deeper than the height of the convex portion T, the raw rubber in the vulcanization process The flow gets worse. For this reason, as shown in FIGS. 10A, 10B, and 10C, a black residue 81 is generated at the edge portion of the convex pattern in the sidewall portion after the polishing process. In FIG. 10D, the remaining black 81 is shown in black.

  FIG. 10D is an enlarged view of a portion of an ellipse 80B in FIG. 10A. When the cover layer 73 shown in FIG. 4 and FIG. 6A does not have the convex portion T, or when the mold does not have the concave portion deeper than the height of the convex portion T, the raw rubber in the vulcanization process The flow gets worse. For this reason, defects such as non-uniform width from the end portion of the black rubber to the end portion of the white rubber may occur in the side wall portion after polishing. For example, as shown in FIG. 10D, the boundary between the black rubber and the white rubber has a wavy shape, or the width H1 from the end of the black rubber to the end of the white rubber exceeds a specified value (for example, 1 mm). To do.

(effect)
On the other hand, in this embodiment, since the convex part is provided on the surface of the rubber sheet 70 and the concave part is provided on the mold, the raw rubber in the vulcanization process can be flowed well, and FIG. 9 and FIG. Unlike the comparative example described with reference to FIG. 10D, defects such as black residue can be prevented.

  The tire 1 described above includes a carcass that extends from the tread portion 6 through the side wall portions 7 on both sides to the bead portion 5, and protrudes from the virtual contour surface 75 along the outer surface of the carcass in the side wall portion 7. (For example, a character, a symbol, or a figure) is formed, and a convex pattern is formed by laminating a rubber layer of a first color and a rubber layer of a second color different from the first color, and one of the rubber layers of the second color The pneumatic tire is exposed in a state where the portion is surrounded by the rubber layer of the first color.

  A tire manufacturing method for manufacturing the tire 1 includes a second color rubber layer (white rubber layer) and a first color rubber layer (black color) that covers the second color rubber layer and has a convex portion on the surface. Forming a rubber sheet 70 including a rubber layer), forming a green tire in which the rubber sheet 70 is disposed outside the carcass of the sidewall portion 7, and gold having a shape corresponding to the convex pattern Heating and pressurizing the green tire in the mold, and cutting the first color rubber layer to expose at least a part of the second color rubber layer.

  The surface of the black rubber layer (first color rubber layer) used in this manufacturing method is provided with a convex shape. Thereby, in the vulcanization process of the green tire, air can be effectively released in the concave portion of the mold, and the raw rubber can be flowed well. Further, the black rubber layer is sufficiently stretched on the inner surface of the mold and disposed in an appropriate amount, and defects such as black residue after the polishing step can be eliminated without increasing the amount of non-black rubber.

  In the above description, the rubber layer of the first color is a black rubber layer and the rubber layer of the second color is a white rubber layer. However, the first color and the second color may be different from each other. It is not limited to.

(Example)
In the buffing process when manufacturing a pneumatic tire with a tire size of 275 / 70R16 114S, after the raised surface is buffed for a certain period of time with an automatic buffing device, an appearance inspection is performed to check whether there is a black residue defect. The rate was measured.

  In Table 1, the “convex forming portion” is, for example, the die 10 of the extrusion molding apparatus described with reference to FIGS. 7A and 7B. The “groove pitch” is, for example, the interval D between the grooves of the cap described with reference to FIG. 7B. The “groove radius” is, for example, the radius R of the cross section of the groove described with reference to FIG. 7B.

  The “mold recess” is, for example, the recess 201 of the molds 200A to 200D described with reference to FIGS. 8A to 8D. The “depth of the recess” is the depth of the recesses B and B11 to B14 described with reference to FIGS. 8A to 8D (depth from the bottom surface 201A of the molds 200A to 200D). The “depth from the mold surface” is, for example, the depth DH of the molds 200A to 200D described with reference to FIGS. 8A to 8D.

  In Table 1, the result is shown as an index where the yield rate of the comparative example is 80% and the comparative example is 100. The larger the value, the higher the yield rate.

  As shown in Example 1 to Example 7 in Table 1, when the groove radius is 0.3 mm or more and 0.5 mm or less and the depth from the mold surface is 3.0 mm or more and 5.5 mm or less, the non-defective product is obtained. It turns out that the rate is high.

DESCRIPTION OF SYMBOLS 1 Tire 2 Bead core 3 Bead filler 4 Carcass layer 5 Belt layer 6 Tread part 7 Side wall part 8 Belt reinforcement layer 10 Base 40 Carcass ply 51 Belt ply 70 Rubber sheet 71, 71L, 71U Black rubber layer 72 White rubber layer 73 Cover layer 74 Undercover layer 75 Virtual contour surface 200A to 200D Mold 70 Rubber sheet 711 End portion 720 Flat surface B, B11 to B14 Recessed portion BH, BH1 to BH4 Vent hole CL Equatorial surface T Convex portion

Claims (12)

A carcass extending from the tread portion to the bead portion through the side wall portions on both sides is formed, and a convex pattern raised from a virtual contour surface along the outer surface of the carcass is formed on the sidewall portion, and the convex pattern is A rubber layer of a first color and a rubber layer of a second color different from the first color are laminated, and a part of the rubber layer of the second color is exposed in a state surrounded by the rubber layer of the first color. A tire manufacturing method for manufacturing a pneumatic tire,
Forming a rubber sheet that includes the rubber layer of the second color and the rubber layer of the first color that covers the second color rubber layer and has a convex portion on the surface;
Forming a green tire in which the rubber sheet is disposed outside the carcass of the sidewall portion;
Heating and pressurizing the green tire in a mold having a shape corresponding to the convex pattern;
Scraping the rubber layer of the first color to expose at least a part of the rubber layer of the second color.   The tire manufacturing method according to claim 1, wherein the convex pattern is composed of characters, symbols, or figures.   The tire manufacturing method according to claim 1 or 2, wherein, in the step of forming the rubber sheet, the convex portion is formed on the rubber sheet using a base having a groove at a discharge port.   The discharge port includes a plurality of the grooves, the plurality of grooves are arranged in a tire width direction, and the convex portion having a shape corresponding to the plurality of the grooves is formed on the rubber sheet. The tire manufacturing method as described.   The tire manufacturing method according to claim 3 or 4, wherein a cross-sectional shape of the groove is a semicircle, and a radius of the semicircle is not less than 0.3 mm and not more than 0.5 mm.   The tire manufacturing method according to any one of claims 1 to 5, wherein the mold has a concave portion deeper than a height of the convex portion at a position corresponding to the convex portion.   The tire manufacturing method according to claim 6, wherein the concave portion is provided at least at a position corresponding to the entire circumference of the edge portion of the convex pattern.   The tire manufacturing method according to claim 6, wherein the recess has a depth from the surface of the mold corresponding to a main molding surface that is a portion other than the convex pattern of 3.0 mm or more and 5.5 mm or less.   The tire manufacturing method according to any one of claims 6 to 8, further comprising a vent hole provided in the recess for discharging air between the mold and the green tire. 10. The tire manufacturing method according to claim 9, wherein one vent hole is provided in the deepest portion of the concave portion per area of 80 mm ² .   The tire manufacturing method according to claim 9, wherein the vent hole is provided at least in the recess.   The metal mold | die used for the tire manufacturing method of any one of Claims 1-11.