Patent Publication Number: US-2023158764-A1

Title: Tread part with color line

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority of Japanese Patent Application No.: 2021-189137 filed on Nov. 22, 2021, the content of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     Technical Field 
     The present invention relates to a tread part with a color line. 
     Related Art 
     As a tread part, a tread part with a color line for identification and/or a color line as a reference line of an assembling position on an outer surface is known. Japanese Patent Application Laid-Open No. 2000-61999 discloses, as a method for manufacturing a tread part with a color line. The method includes a step of extruding a rubber material into a predetermined cross-sectional shape from a mouthpiece to form a tread part with a protrusion extending along an extrusion direction on an outer surface, and a step of transferring and applying color rubber cement to a top of the protrusion by a wide transfer roller. 
     SUMMARY 
     In the method of Japanese Patent Application Laid-Open No. 2000-61999, by applying a color line by the transfer roller, even when the extruded rubber meanders, the color line is stably applied to the protrusion of the tread part by the wide transfer roller. However, the method of Japanese Patent Application Laid-Open No. 2000-61999 applies color rubber by the transfer roller, and cannot be applied when color rubber is applied using a nozzle. 
     An object of the present invention is to provide a tread part with a color line in which color rubber can be stably applied to the tread part using a nozzle. 
     An object of one aspect of the present invention is to provide a tread part with a color line. The tread part is a rubber extruded shape having a predetermined cross-sectional shape and extending in a first direction. The tread part has a first main surface that constitutes an outer peripheral surface of a green tire in a tire radial direction when the tread part is wound in a cylindrical shape. The tread has a pair of opposing wall surfaces that extend in the first direction on the first main surface and face each other in a second direction orthogonal to the first direction. The tread has color rubber extending in the first direction between the pair of opposing wall surfaces on the first main surface. 
     According to the present invention, when the color rubber is applied to the tread part by nozzle, even if the tread part meanders in a width direction, a tip of the nozzle is easily held between the pair of the opposing wall surfaces. The color rubber is easily applied between the pair of the opposing wall surfaces. That is, since the color rubber can be applied to the tread part while meandering is suppressed, in a pneumatic tire vulcanization molded using the tread part, meandering of a color line made from the color rubber is suppressed. Therefore, the color rubber can be stably applied to the tread part using the nozzle. 
     A color rubber width dimension which is a length in the second direction of the color rubber may be 67% or more and 133% or less of a wall surface interval which is a length in the second direction on the first main surface between the pair of the opposing wall surfaces. 
     According to the present configuration, the nozzle for applying the color rubber is easily arranged between the pair of the opposing wall surfaces. When the color rubber width dimension exceeds 133% of the wall surface interval, it is difficult to arrange the nozzle between the pair of the opposing wall surfaces. When the color rubber width dimension is less than 67% of the wall surface interval, the nozzle can move in the width direction of the tread part between the pair of the opposing wall surfaces, so that meandering of the color rubber applied between the pair of the opposing wall surfaces is likely to increase. 
     A height of the pair of the opposing wall surfaces in a direction orthogonal to the first main surface may be 3 mm or more and 4.5 mm or less. 
     According to the present configuration, the nozzle for applying the color rubber is easily held between the pair of the opposing wall surfaces. When the height of the pair of the opposing wall surfaces is less than 3 mm, retention of the nozzle by the pair of the opposing wall surfaces is deteriorated. When the height of the pair of the opposing wall surfaces exceeds 4.5 mm, a portion constituting the pair of the opposing wall surfaces tend to flow so as to cover the color rubber at the time of vulcanization molding, and discriminability by the color rubber is deteriorated. 
     The tread part may have a pair of protrusions protruding from the first main surface and extending in the first direction, and the pair of the opposing wall surfaces may be constituted by a pair of side surfaces facing each other in the second direction among side surfaces of the pair of the protrusions. 
     The pair of the protrusions may have a triangular cross-sectional shape. 
     According to the present configuration, the pair of the protrusions can easily configure the pair of the opposing wall surfaces. As compared with a case where a pair of the opposing wall surfaces are constituted by a groove, it is easy to secure an amount of rubber, and it is easy to suppress rubber chipping due to an insufficient amount of rubber at the time of vulcanization molding. 
     The wall surface interval may be 1.5 mm or more and 6.0 mm or less. 
     According to the present configuration, since the wall surface interval is 1.5 mm or more and 6.0 mm or less, for example, the nozzle for applying color rubber having a color rubber width dimension of 2.0 mm or more and 4.0 mm or less is easily arranged between the pair of the opposing wall surfaces. In this manner, a color line for the color rubber applied between the pair of the opposing wall surfaces can form part identification. 
     The wall surface interval may be 0.20 mm or more and 1.50 mm or less. 
     According to the present configuration, since the wall surface interval is 0.20 mm or more and 1.50 mm or less, for example, the nozzle for applying the color rubber having a color rubber width dimension of 0.25 mm or more and 1.00 mm or less is easily arranged between the pair of the opposing wall surfaces. In this manner, the color rubber applied between the pair of the opposing wall surfaces can configure a reference line serving as a reference of an assembling position when assembling a green tire. 
     In the cross-sectional shape, the pair of the opposing wall surfaces may be at an angle of 60° or more and 90° or less with respect to the first main surface to be orthogonal to the first main surface or inclined in a direction in which the pair of the opposing wall surfaces are separated from each other. 
     According to the present configuration, since a region defined between the pair of the opposing wall surfaces, to which the color rubber is applied is set to an appropriate size, a usage amount of the color rubber is optimized. 
     According to the present invention, in manufacturing a tread member with a color line, color rubber can be stably applied using a nozzle while meandering of the color rubber with respect to the tread part is suppressed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and the other features of the present invention will become apparent from the following description and drawings of an illustrative embodiment of the invention in which: 
         FIG.  1    is a schematic view of an apparatus for manufacturing a tread part according to a first embodiment of the present invention; 
         FIG.  2    is a front view of a mouthpiece according to an arrow A in  FIG.  1   ; 
         FIG.  3    is a perspective view of a tread part; 
         FIG.  4    is a perspective view illustrating application of color rubber to the tread part by a nozzle; 
         FIG.  5    is a cross-sectional view illustrating a pair of side protrusions taken along line V-V of  FIG.  4    together with the nozzle; 
         FIG.  6    is a cross-sectional view of a pair of center protrusions, like  FIG.  5   ; 
         FIG.  7    is a diagram schematically illustrating a step of winding the tread part around a forming drum; 
         FIG.  8    is a perspective view schematically illustrating a green tire; 
         FIG.  9    is a front view of the mouthpiece according to a second embodiment; 
         FIG.  10    is a cross-sectional view similar to  FIG.  5    and illustrating the tread part extruded from the mouthpiece of  FIG.  9   ; 
         FIG.  11    is a front view of the mouthpiece according to a third embodiment; and 
         FIG.  12    is a cross-sectional view similar to  FIG.  5    and illustrating the tread part extruded from the mouthpiece of  FIG.  11   . 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Hereinafter, an embodiment according to the present invention will be described with reference to the accompanying drawings. Note that description below is merely exemplary in nature and is not intended to limit the present invention, its application, or its use. 
     First Embodiment 
       FIG.  1    schematically illustrates a tread production line  10  for producing a tread part  1 . As illustrated in  FIG.  1   , the tread production line  10  includes an extruder  11  that extrudes a rubber material R into a predetermined cross-sectional shape to form the tread part  1 , and nozzles  16  and  17  that apply color rubber  30  (see  FIG.  3   ) to the tread part  1 . 
     The extruder  11  includes a hopper  12  into which the rubber material R is supplied, a screw  13  that conveys the rubber material R supplied into the hopper  12  while kneading the rubber material R, a drive source  14  (for example, a motor) that drives the screw  13 , and a mouthpiece  20 . The extruder  11  rotates the screw  13  by driving of the drive source  14  to knead and heat the rubber material R, and extrudes the rubber material R from the mouthpiece  20  in an extrusion direction E (first direction). The extruded rubber material R constitutes the tread part  1  which is an elongated strip-shaped extruded part having a predetermined cross-sectional shape. 
     The nozzles  16  and  17  are located on the downstream side in the extrusion direction E with respect to the extruder  11 , and apply the color rubber  30  to a surface of the tread part  1  to be conveyed. 
       FIG.  2    is a front view of the mouthpiece  20  as viewed from an arrow A in  FIG.  1   . As illustrated in  FIG.  2   , the mouthpiece  20  has a laterally long opening  21 . The opening  21  has an opening upper surface  22  and an opening bottom surface  23  extending in a left-right direction (second direction) orthogonal to the extrusion direction E, and a pair of opening side surfaces  24  extending in a vertical direction. The opening upper surface  22  is shorter than the opening bottom surface  23  in the left-right direction. The pair of the opening side surfaces  24  connect left and right side portions of the opening upper surface  22  and left and right side portions of the opening bottom surface  23 , respectively. The opening  21  is formed in a trapezoidal shape that is bilaterally symmetrical with respect to a center line CL in the left-right direction. The rubber material R is extruded in a trapezoidal cross-sectional shape through the opening  21  of the mouthpiece  20 . 
     The opening upper surface  22  is formed with a notch  25  recessed upward and extending in the extrusion direction E. In the present embodiment, the mouthpiece  20  has, as the notch  25 , a pair of left and right side notches  26  formed on the left side of the opening upper surface  22  and a pair of left and right center notches  27  formed at the center in the left-right direction of the opening upper surface  22 . In the present embodiment, the side notch  26  and the center notch  27  are formed in a triangular cross section by, for example, marking the opening upper surface  22  in the extrusion direction E. In addition, the side notch  26  and the center notch  27  may be formed in an optional cross-sectional shape such as a rectangular shape, a trapezoidal shape, a semicircular shape, or a curved shape. 
     Each of the pair of the side notches  26  has a recess amount H 1  from the opening upper surface  22  of 3 mm or more and 4.5 mm or less. The notch  26  is at an angle K 1  with respect to the opening upper surface  22  of 90° or inclined at 60° or more in a direction in which the side notches  26  are separated from each other. A distance D 1  in the left-right direction between the pair of the side notches  26  is 1.5 mm or more and 6.0 mm or less. 
     Similarly, each of the pair of the center notches  27  has a recess amount H 2  from the opening upper surface  22  of 3 mm or more and 4.5 mm or less. The notch  27  is at an angle K 2  with respect to the opening upper surface  22  of 90° or inclined at 60° or more in a direction in which the center notches  27  are separated from each other. A distance D 2  in the left-right direction between the pair of the center notches  27  is 0.20 mm or more and 1.50 mm or less. 
       FIG.  3    is a perspective view of the tread part  1 . The tread part  1  has a cross-sectional shape corresponding to the shape of the opening  21  of the mouthpiece  20 . The tread part  1  has a first main surface  2  formed by the opening upper surface  22 , a second main surface  3  formed by the opening bottom surface  23 , and a pair of tread side surfaces  4  formed by the pair of the opening side surfaces  24 . In  FIG.  3   , the first main surface  2  and the second main surface  3  extend in the left-right direction. The first main surface  2  is shorter in the left-right direction than the second main surface  3 . The pair of the tread side surfaces  4  vertically connects left and right side portions of the first main surface  2  and left and right side portions of the second main surface  3 . The tread part  1  is an elongated extruded shape having a laterally long cross-sectional shape and extending in the extrusion direction E. 
     The first main surface is formed with protrusions  5  extending in the extrusion direction E. The protrusions  5  include a pair of side protrusions  6  formed by the pair of the side notches  26  and a pair of center protrusions  7  formed by the pair of the center notches  27 . 
       FIG.  4    is a perspective view illustrating a portion around a tip  16   a  of the nozzle  16 . As illustrated in  FIG.  4   , the tip  16   a  of the nozzle  16  is positioned between the pair of the side protrusions  6 . When the color rubber  30  is supplied from the nozzle  16 , the color rubber  30  is applied between the pair of the side protrusions  6  on the first main surface  2 . The color rubber  30  is applied onto the first main surface  2  as the tread part  1  is conveyed in the extrusion direction E, and thus the color rubber  30  extends on the downstream side in the extrusion direction E with respect to the nozzle  16 . 
       FIG.  5    is a cross-sectional view taken along line V-V in  FIG.  4   , and is a cross-sectional view of the tread part  1  when the pair of the side protrusions  6  and the nozzle  16  positioned between them are viewed from the extrusion direction E. The pair of the side protrusions  6  are formed in a triangular cross section corresponding to a shape of the pair of the side notches  26 . Each of the pair of the side protrusions  6  has a protrusion amount X 1  from the first main surface  2  of 3 mm or more and 4.5 mm or less. The side protrusion  6  is at an angle Y 1  with respect to the first main surface  2  of 90° or is inclined at 60° or more in a direction in which the side protrusions  6  are separated from each other. An inner diameter W 1  of the nozzle  16  is 67% or more and 133% or less of a distance Z 1  (wall surface interval) in the left-right direction on the first main surface  2  between the pair of the side protrusions  6 . The inner diameter W 1  of the nozzle  16  is 2.0 mm or more and 4.0 mm or less. Therefore, the distance Z 1  between a pair of opposing wall surfaces  6   a  on the first main surface  2  is 1.5 mm or more and 6.0 mm or less. 
     In the present embodiment, since the inner diameter W 1  of the nozzle  16  is 3.0 mm, the distance Z 1  between the pair of the side protrusions  6  is 2 mm or more and 4 mm or less. In other words, the distance D 1  between the pair of the side notches  26  in the mouthpiece  20  is set such that the distance Z 1  between the pair of the side protrusions  6  falls within the above range. The pair of the side protrusions  6  has the opposing wall surfaces  6   a  facing each other in a width direction (left-right direction in  FIG.  5   ). 
     The tip  16   a  of the nozzle  16  is located above the first main surface  2  and below an apex of the pair of the side protrusions  6 . That is, the tip  16   a  of the nozzle  16  is sandwiched in the left-right direction by the pair of the side protrusions  6 , that is, the pair of the opposing wall surfaces  6   a . In the present embodiment, the distance Z 1  between the pair of the side protrusions  6  is set to 2.0 mm. When the color rubber  30  is supplied from the nozzle  16 , a side color line  31  extending in the extrusion direction E with a width F 1  (color rubber width dimension) corresponding to the inner diameter W 1  of the nozzle  16  is formed between the pair of the side protrusions  6  on the first main surface  2 . In the present embodiment, the width F 1  of the side color line  31  is substantially equal to the inner diameter W 1  of the nozzle  16 , and it is 2.0 mm or more and 4.0 mm or less. 
     Similarly,  FIG.  6    is a cross-sectional view of the tread part  1  when the pair of the center protrusions  7  and the nozzle  17  positioned between them are viewed from the extrusion direction E. The pair of the center protrusions  7  are formed in a triangular cross section corresponding to a shape of the pair of the center notches  27 . Each of the pair of the center protrusions  7  has a protrusion amount X 2  from the first main surface  2  of 3 mm or more and 4.5 mm or less. The center protrusion  7  is at an angle Y 2  with respect to the first main surface  2  of 90° or is inclined at 60° or more in a direction in which the center protrusions  7  are separated from each other. An inner diameter W 2  of the nozzle  17  is 67% or more and 133% or less of a distance Z 2  (wall surface interval) in the left-right direction on the first main surface  2  between the pair of the center protrusions  7 . The inner diameter W 2  of the nozzle  17  is 0.25 mm or more and 1.00 mm or less. Therefore, the distance Z 2  between a pair of opposing wall surfaces  7   a  on the first main surface  2  is 0.20 mm or more and 1.50 mm or less. 
     In the present embodiment, since the inner diameter W 2  of the nozzle  17  is 0.5 mm, the distance Z 2  between the pair of the center protrusions  7  is 0.3 mm or more and 0.7 mm or less. In other words, the distance D 2  between the pair of the center notches  27  in the mouthpiece  20  is set such that the distance Z 2  between the pair of the center protrusions  7  falls within the above range. The pair of the center protrusions  7  has the opposing wall surfaces  7   a  facing each other in the width direction (left-right direction in  FIG.  6   ). 
     A tip  17   a  of the nozzle  17  is located above the first main surface  2  and below an apex of the pair of the center protrusions  7 . That is, the tip  17   a  of the nozzle  17  is sandwiched in the left-right direction by the pair of the center protrusions  7 , that is, the pair of the opposing wall surfaces  7   a . In the present embodiment, the distance Z 2  between the pair of the center protrusions  7  is set to 0.25 mm. When the color rubber  30  is supplied from the nozzle  17 , a center color line  32  extending in the extrusion direction E with a width F 2  (color rubber width dimension) corresponding to the inner diameter W 2  of the nozzle  17  is formed between the pair of the center protrusions  7  on the first main surface  2 . In the present embodiment, the width F 2  of the center color line  32  is substantially equal to the inner diameter W 2  of the nozzle  17 , and it is 0.25 mm or more and 1.00 mm or less. 
       FIG.  7    schematically illustrates a step of forming a tread ring  51  by winding the tread part  1  in which the side color line  31  and the center color line  32  are applied to the first main surface  2  in a cylindrical shape on a forming drum  40 . The forming drum  40  rotates about a central axis O 1  so that the tread part  1  is wound around an outer peripheral portion. A belt  52  is wound on the forming drum  40  in advance. The tread part  1  is wound on an outer peripheral surface of the belt  52 . 
     At this time, the tread part  1  is wound with a longitudinal direction along a circumferential direction of the forming drum  40  in a posture in which the first main surface  2  is located on the outer peripheral side. In this manner, the tread part  1  is wound in a cylindrical shape such that the side color line  31  and the center color line  32  extend along the outer periphery of the forming drum  40  on the outer peripheral surface. 
     The forming drum  40  is provided with a laser marker  41  that irradiates a central portion in the width direction with a laser beam. The tread part  1  is wound with the center color line  32  coinciding with a laser beam L emitted from the laser marker  41  toward the forming drum  40  in the width direction of the forming drum  40 . In this manner, the tread part  1  is easily wound accurately with respect to the forming drum  40  in a manner that positional deviation in the width direction of the forming drum  40  is suppressed. That is, the center color line  32  constitutes a reference line that is a reference of an assembling position when the tread part  1  is assembled to the forming drum  40 . 
       FIG.  8    is a perspective view of a green tire  50  formed by expanding a separately molded carcass band  53  toward the outer diameter side in a toroidal shape and attaching the carcass band  53  to an inner peripheral surface of the tread ring  51 . As illustrated in  FIG.  8   , an outer peripheral surface  50   a  of the green tire  50  is constituted by the first main surface  2  of the tread part  1 , and the side color line  31  and the center color line  32  extend in a circumferential direction of the green tire  50 . 
     A type of the green tire  50  can be identified by a color, width, position in a tire axial direction, and the like of the side color line  31 . Therefore, the side color line  31  constitutes a color line for identification to identify a type of the tread part  1 , the green tire  50 , and a pneumatic tire (not illustrated) obtained by vulcanization molding the green tire  50 . 
     According to the tread part  1  and the method for manufacturing the tread part  1  according to the above embodiment, operation and effect described below are achieved. Hereinafter, the operation and effect of the pair of the opposing wall surfaces  6   a  and the side color line  31  will be described. However, the same operation and effect are obtained for the pair of the opposing wall surfaces  7   a  and the center color line  32  unless otherwise specified, and description of them will be omitted. 
     (1) The tread part  1  is a rubber extruded shape having a predetermined cross-sectional shape and extending in the extrusion direction E. The tread part  1  has the first main surface  2  that constitutes the outer peripheral surface  50   a  of the green tire  50  in a tire radial direction when the tread part  1  is wound in a cylindrical shape. The tread part  1  has the pair of the opposing wall surfaces  6   a  that extend in the extrusion direction E on the first main surface  2  and face each other in the width direction orthogonal to the extrusion direction E. The tread part  1  has the side color line  31  extending in the extrusion direction E between the pair of the opposing wall surfaces  6   a  on the first main surface  2 . 
     That is, in the method for manufacturing the tread part  1  with the side color line  31 , the rubber material R is extruded from the mouthpiece  20  into a predetermined cross-sectional shape in the extrusion direction E. The tread part  1  has the first main surface  2  constituting the outer peripheral surface  50   a  of the green tire  50  in the tire radial direction when the rubber material R is wound in a cylindrical shape. The pair of the opposing wall surfaces  6   a  extending in the extrusion direction E on the first main surface  2  and facing each other in the left-right direction orthogonal to the extrusion direction E is formed. The color rubber  30  is applied onto the first main surface  2  by the nozzle  16  arranged between the pair of the opposing wall surfaces  6   a  with respect to the tread part  1  conveyed in the extrusion direction E to form the side color line  31 . 
     As a result, when the color rubber  30  is applied to the tread part  1  by positioning the nozzle  16  between the pair of the opposing wall surfaces  6   a , even if the tread part  1  meanders in the width direction, the tip  16   a  of the nozzle  16  is easily held between the pair of the side protrusions  6 . The color rubber  30  is easily applied between the pair of the opposing wall surfaces  6   a . That is, since the color rubber  30  can be applied to the tread part  1  while meandering is suppressed, meandering of the side color line  31  made from the color rubber  30  is suppressed in a pneumatic tire vulcanization molded using the tread part  1 . Therefore, the color rubber  30  can be stably applied to the tread part  1  using the nozzle  16 . 
     As in the case of using a plurality of rubber materials having different characteristics in the width direction of the tread part  1  as the rubber material R, the above operation and effect are suitably exhibited. In particular, in the case where the tread part  1  is likely to meander in the width direction at an initial stage until the extrusion of the tread part  1  is stabilized, the above operation and effect are suitably exhibited. 
     (2) The width F 1  of the side color line  31  is 67% or more and 133% or less of the distance Z 1  between the pair of the opposing wall surfaces  6   a . As a result, the nozzle  16  is easily arranged between the pair of the opposing wall surfaces  6   a . When the width F 1  of the side color line  31  exceeds 133% of the distance Z 1  between the pair of the opposing wall surfaces  6   a , it is difficult to arrange the nozzle  16  between the pair of the opposing wall surfaces  6   a . When the width F 1  of the side color line  31  is less than 67% of the distance Z 1  between the pair of the opposing wall surfaces  6   a , a movement allowance of the nozzle  16  in the width direction of the tread part  1  between the pair of the opposing wall surfaces  6   a  increases. As a result, meandering of the side color line  31  between the pair of the opposing wall surfaces  6   a  is likely to increase. 
     (3) A height of the pair of the side protrusions  6 , that is, the opposing wall surfaces  6   a  in a direction orthogonal to the first main surface  2  is 3 mm or more and 4.5 mm or less. As a result, the nozzle  16  is easily held between the pair of the opposing wall surfaces  6   a . When the height of the pair of the opposing wall surfaces  6   a  is less than 3 mm, retention of the nozzle  16  by the pair of the opposing wall surfaces  6   a  is deteriorated. If the height of the pair of the opposing wall surfaces  6   a  exceeds 4.5 mm, the pair of the side protrusions  6  flow so as to cover the side color line  31  at the time of vulcanization molding and the side color line  31  is easily embedded, and the distinguishability by the side color line  31  is deteriorated. 
     (4) The pair of the opposing wall surfaces  6   a  is constituted by the pair of side surfaces facing each other in the width direction in the pair of the side protrusions  6 . As a result, the pair of the side protrusions  6  can easily configure the pair of the opposing wall surfaces  6   a . As compared with a case where a pair of the opposing wall surfaces are constituted by a groove, it is easy to secure an amount of rubber, and rubber chipping due to an insufficient amount of rubber is suppressed at the time of vulcanization molding. 
     (5) Regarding the pair of the side protrusions  6 , the distance Z 1  between the pair of the opposing wall surfaces  6   a  is 1.5 mm or more and 6.0 mm or less. Accordingly, for example, the nozzle  16  for applying the color rubber  30  having a color rubber width dimension of 2.0 mm or more and 4.0 mm or less is easily arranged between the pair of the opposing wall surfaces  6   a . In this manner, a color line for part identification can be configured using the side color line  31  formed by the color rubber  30  applied between the pair of the opposing wall surfaces  6   a . When the width of the side color line  31  is less than 2.0 mm, the pair of the side protrusions  6  flow to cover the side color line  31  at the time of vulcanization molding and the side color line  31  is likely to be embedded, and discriminability by the side color line  31  is deteriorated. When the width of the side color line  31  exceeds 4.0 mm, there is a possibility of occurring a defect in which the side color line  31  is transferred to the mold at the time of vulcanization molding. 
     (6) Regarding the pair of the center protrusions  7 , the distance Z 2  between the pair of the opposing wall surfaces  7   a  is 0.20 mm or more and 1.50 mm or less. Accordingly, for example, the nozzle  17  for applying the color rubber  30  having a color rubber width dimension of 0.25 mm or more and 1.00 mm or less is easily arranged between the pair of the opposing wall surfaces  7   a . In this manner, a reference line that is a reference of an assembling position when a green tire is assembled using the center color line  32  formed by the color rubber  30  applied between the pair of the opposing wall surfaces  7   a  can be configured. When the width F 2  of the center color line  32  is less than 0.25 mm, it is difficult to stably apply the color rubber by the nozzle  17 . If the width F 2  of the center color line  32  exceeds 1.00 mm, the reference line at the assembling position is too thick, and thus the assembling accuracy is likely to deteriorate. 
     (7) The angle Y 1  of the opposing wall surfaces  6   a  of the pair of the side protrusions  6  with respect to the first main surface  2  is 60° or more and 90° or less. In other words, the pair of the opposing wall surfaces  6   a  are orthogonal to or inclined in a direction in which the opposing wall surfaces  6   a  are separated from each other with respect to the first main surface  2 . As a result, a region, defined between the pair of the opposing wall surfaces  6   a  to which the color rubber  30  is applied is set to an appropriate size. Accordingly, the usage amount of the color rubber  30  is optimized. As the angle Y 1  is larger, that is, closer to 90°, the region to which the color rubber  30  is applied is smaller, and the usage amount of the color rubber  30  is reduced. 
     Second Embodiment 
       FIG.  9    is a front view similar to  FIG.  2    of a mouthpiece  60  according to a second embodiment, and  FIG.  10    is an enlarged view similar to  FIG.  5    of a tread part  70  extruded from the mouthpiece  60 . As illustrated in  FIG.  9   , the mouthpiece  60  is different from the mouthpiece  20  in that a projections  65  protruding downward on an opening top surface  62  and extending in the extrusion direction E are provided instead of the notch  25 . 
     In the present embodiment, the mouthpiece  60  includes, as the projections  65 , a side projection  66  formed on the left side and a center projection  67  formed at the center in the left-right direction of the opening top surface  62 . The side projection  66  and the center projection  67  are formed in a trapezoidal shape in which a distance in the left-right direction decreases downward. In addition, the side projection  66  and the center projection  67  may have any cross-sectional shape such as a rectangular shape, a triangular shape, a semicircular shape, or a curved shape. 
     As illustrated in  FIG.  10   , in the tread part  70 , a side groove  76  recessed downward with respect to a tread top surface  71  is formed by the side projection  66 . The side groove  76  is recessed in a trapezoidal shape and has a pair of opposing wall surfaces  76   a  facing each other in the left-right direction. The tip  16   a  of the nozzle  16  is arranged between the pair of the opposing wall surfaces  76   a . Although not illustrated, a center groove recessed downward in a trapezoidal shape is formed on the tread top surface  71  by the center projection  67 , and the tip  17   a  of the nozzle  17  is arranged between the pair of opposing wall surfaces defining the center groove. 
     According to the present embodiment, the pair of the opposing wall surfaces  76   a  can be easily configured by the side groove  76 . An increase in an amount of rubber can be suppressed as compared with the case where the pair of the opposing wall surfaces  6   a  are constituted by the pair of the side protrusions  6  in the first embodiment. 
     Third Embodiment 
       FIG.  11    is a front view similar to  FIG.  2    of a mouthpiece  80  according to a third embodiment, and  FIG.  12    is an enlarged view similar to  FIG.  5    of a tread part  90  extruded from the mouthpiece  80 . As illustrated in  FIG.  11   , the mouthpiece  80  is different from the mouthpiece  20  in that a projections  85  protruding downward on an opening top surface  82  and extending in the extrusion direction E are provided. 
     In the present embodiment, the mouthpiece  80  includes, as the projections  85 , a side projection  86  formed between the pair of the side notches  26 , and a center projection  87  formed between the pair of the center notches  27 . The side projection  86  and the center projection  87  are formed in a trapezoidal shape in which a distance in the left-right direction decreases downward to be continuous with both side surfaces of the side notch  26  and the center notch  27  facing each other. In addition, the side projection  86  and the center projection  87  may have any cross-sectional shape such as a rectangular shape, a triangular shape, a semicircular shape, or a curved shape. 
     As illustrated in  FIG.  12   , the tread part  90  has a pair of side protrusions  96  formed so as to protrude upward from a tread top surface  91  by the pair of the side notches  26 , and the side groove  97  formed so as to be recessed downward from the tread top surface  91  by the side projection  86 . Side surfaces of the pair of the side protrusions  96  facing each other and side surfaces of the side groove  97  facing each other are continuous in the vertical direction, and constitute a pair of opposing wall surfaces  96   a . The tip  16   a  of the nozzle  16  is arranged between the pair of the opposing wall surfaces  96   a . Although not illustrated, a pair of center protrusions and a center groove are similarly formed by the pair of the center notches  27  and the center projection  87 , and the tip  17   a  of the nozzle  17  is arranged between their opposing wall surfaces facing each other. 
     According to the present embodiment, the pair of the opposing wall surfaces  96   a  can be easily configured by the pair of the side protrusions  96  and the side groove  97 . In particular, it is easy to set a height of the side protrusion  96  to be low and a depth of the side groove  97  to be small, and it is easy to achieve both securing of an amount of rubber and suppressing an increase in the amount of rubber. 
     It should be noted that the present invention is not limited to the configuration described in the above embodiment, and various modifications are possible. 
     In the above embodiment, the case where both the side color line  31  and the center color line  32  are provided is described as an example, but the present invention is not limited to this example. For example, the present invention can be applied to various cases such as a case where only the center color line  32  is provided, a case where only the side color line  31  is provided, and a case where a plurality of the side color lines  31  are provided.