Tire molding die

Abstract

This invention provides a tire molding die that suppresses the occurrence of black residue defects and enables the production of pneumatic tires with a good appearance. [Solution] The tire molding die 10 according to this embodiment includes a lower side plate 1 for molding the side portion of the tire 100, and a recess 20 provided on the lower side plate 1, having a bottom surface 21 and a wall surface 22 that contact the cover rubber layer 71 of the tire 100, and for molding the white rubber layer 72 of the tire 100 that protrudes from the side portion and is covered by the cover rubber layer 71. The recess 20 has an outer region 30 located on the outer side in the radial direction of the mold with respect to the mold radial center CL of the recess 20, and the cross-sectional area of ​​the inner region located on the inner side in the radial direction of the mold is larger than the cross-sectional area of ​​the inner region located on the inner side in the radial direction of the mold.

Description

Technical Field

[0001] The present invention relates to a tire molding die.

Background Art

[0002] Conventionally, from the viewpoint of decoration, there are white ribbon tires having a ring-shaped white decoration on the side portion of a tire, and white letter tires having white letters indicating a manufacturer name, a brand name, etc. (for example, see Patent Document 1). Such white display items such as decorations and letters are formed by a white rubber layer protruding from the side portion of an inflated tire. This type of inflated tire includes a green tire including a white rubber layer at at least a part of the side portion and a black cover rubber layer covering the white rubber layer, and is vulcanized by being put into a tire molding die having recesses corresponding to the white rubber layer and the cover rubber layer. It is manufactured through a process of exposing the white rubber layer formed in the recess by polishing (buffing) and removing the cover rubber layer.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in such a method for manufacturing an inflated tire, when the tire is vulcanized, the white rubber layer does not uniformly contact the tire molding die, and the formed white rubber layer undulates, so that even when the cover rubber layer is polished, it may not be sufficiently removed and may remain on the display item. The phenomenon that the cover rubber layer remains on the display item is called black residue defect, which causes deterioration of the appearance of the inflated tire.

[0005] The present invention aims to provide a tire molding die that can suppress the occurrence of black residue defects and produce pneumatic tires with a good appearance. [Means for solving the problem]

[0006] The tire molding die according to the present invention comprises a side plate for molding the side portion of a tire, and a recess provided on the side plate, having a bottom surface and wall surface that contact the first colored rubber layer of the tire, and protruding from the side portion for molding the second colored rubber layer of the tire which is covered by the first colored rubber layer, wherein the cross-sectional area of ​​the outer region located on the radial side of the mold with respect to the radial center of the mold is larger than the cross-sectional area of ​​the inner region located on the radial side of the mold.

[0007] With this configuration, the cross-sectional area of ​​the outer region of the recess is larger than the cross-sectional area of ​​the inner region relative to the radial center of the mold, allowing the first and second colored rubber layers to flow well into the outer region of the recess. As a result, the second colored rubber layer makes uniform contact with the recess of the tire molding die via the first colored rubber layer, reducing the waviness of the second colored rubber layer. This suppresses the occurrence of black residue defects, enabling the manufacture of tires with a good appearance.

[0008] In the tire molding die according to the present invention, the recess may satisfy the relationship 1.1 ≤ Sh / Sl, where Sh is the cross-sectional area of ​​the outer region and Sl is the cross-sectional area of ​​the inner region. With this configuration, the cross-sectional area of ​​the outer region can be made even larger than the cross-sectional area of ​​the inner region, thereby suppressing the occurrence of black residue defects and enabling the manufacture of tires with a good appearance.

[0009] Furthermore, in the tire molding die according to the present invention, the depth of the recess to the bottom surface in the outer region may be greater than the depth to the bottom surface in the inner region.

[0010] This configuration allows for the creation of a recess where the cross-sectional area of ​​the outer region is larger than the cross-sectional area of ​​the inner region, using a simple structure.

[0011] Further, in the tire molding die according to the present invention, when the maximum depth from the bottom surface in the outer region is Dh and the maximum depth from the bottom surface in the inner region is Dl for the concave portion, the maximum depth in the outer region and the maximum depth in the inner region may each be 3 mm or more and 6 mm or less, and Dl < Dh may be satisfied.

[0012] According to this configuration, it is possible to set an appropriate amount of the white rubber layer as the second color rubber layer formed by the concave portion, and it is possible to suppress an increase in cost and the occurrence of black residue defects due to rubber shortage in the white rubber layer.

[0013] Further, in the tire molding die according to the present invention, the concave portion may have a protrusion protruding inward of the concave portion on at least a part of the bottom surface, and the cross-sectional area of the protrusion in the inner region may be larger than the cross-sectional area of the protrusion in the outer region.

[0014] According to this configuration, a concave portion in which the cross-sectional area of the outer region is larger than the cross-sectional area of the inner region can be created with a simple configuration.

[0015] Further, in the tire molding die according to the present invention, for the concave portion, the wall angle of the wall surface on the outer side in the die radial direction with respect to the perpendicular line from the end portion on the outer side in the die radial direction to the profile surface of the tire may be larger than the wall angle of the wall surface on the inner side in the die radial direction with respect to the perpendicular line from the end portion on the inner side in the die radial direction to the profile surface of the tire.

[0016] According to this configuration, a concave portion in which the cross-sectional area of the outer region is larger than the cross-sectional area of the inner region can be created with a simple configuration. [[ID=​​​​​With this configuration, the rubber flows well into the outer region, and the white rubber layer, acting as the second color rubber layer, makes uniform contact with the recesses of the tire molding die. As a result, the waviness of the white rubber layer is reduced, which suppresses the occurrence of black residue defects and allows for the production of tires with a good appearance.

[0019] Furthermore, in the tire molding die according to the present invention, the wall angle of the inner wall surface in the radial direction of the die with respect to the perpendicular line from the inner end in the radial direction of the die to the profile surface of the tire may be 0° or more and 10° or less.

[0020] With this configuration, the rubber flows smoothly from the inner region to the outer region, and the white rubber layer, acting as the second color rubber layer, makes uniform contact with the recesses of the tire molding die. As a result, the waviness of the white rubber layer is reduced, which suppresses the occurrence of black residue defects and allows for the production of tires with a good appearance.

[0021] Furthermore, in the tire molding die according to the present invention, the recess may have at least one bend groove extending in the circumferential direction of the die on its bottom surface.

[0022] With this configuration, during vulcanization, the bend grooves efficiently guide residual gas from the shallower side of the recess to the deeper side, and it is sufficiently discharged from between the tire and the tire molding die. As a result, the white rubber layer, which acts as the second color rubber layer, makes uniform contact with the recess of the tire molding die via the cover rubber layer, which acts as the first color rubber layer. This reduces the waviness of the white rubber layer, suppressing the occurrence of black residue defects and enabling the production of tires with a good appearance.

[0023] Furthermore, in the tire molding die according to the present invention, the recess may be configured to extend continuously in at least a portion of the circumferential direction of the die, forming a ribbon or part of a character using the second colored rubber layer.

[0024] This configuration allows for improved molding accuracy of white ribbons or white letters formed by the white rubber layer acting as the second color rubber layer. [Effects of the Invention]

[0025] According to an aspect of the present invention, there is provided a tire molding die capable of suppressing the occurrence of black residue defects and manufacturing a pneumatic tire with a good appearance.

Brief Description of the Drawings

[0026] [Figure 1] FIG. 1 is a cross-sectional view showing an example of a tire molding die according to the first embodiment. <( [Figure 2] FIG. 2 is a cross-sectional view showing an example of a recess of the tire molding die according to the first embodiment. [[ID=)15]] [Figure 3] FIG. 3 is a cross-sectional view showing another example of a recess of the tire molding die according to the first embodiment. [Figure 4] FIG. 4 is a cross-sectional view showing another example of a recess of the tire molding die according to the first embodiment. [Figure 5] FIG. 5 is a cross-sectional view showing an example of a wall surface on the outer side in the die radial direction in a recess of the tire molding die according to the first embodiment. [Figure 6] FIG. 6 is a cross-sectional view showing an example of a wall surface on the inner side in the die radial direction in a recess of the tire molding die according to the first embodiment. [Figure 7] FIG. 7 is a cross-sectional view showing an example of a protrusion before polishing of a pneumatic tire molded by the tire molding die according to the first embodiment. [Figure 8] FIG. 8 is a cross-sectional view showing an example of a protrusion after polishing of a pneumatic tire molded by the tire molding die according to the first embodiment. [Figure 9] FIG. 9 is a cross-sectional view showing an example of a recess of the tire molding die according to the second embodiment. [Figure 10] FIG. 10 is a cross-sectional view showing another example of a recess of the tire molding die according to the second embodiment. [Figure 11] FIG. 11 is a cross-sectional view showing another example of a recess of the tire molding die according to the second embodiment. [[ID=4*3]] [Figure 12] FIG. 12 is a partially enlarged cross-sectional view of a recess showing an example of a bend groove formed in a recess of the tire molding die according to the second embodiment. [Figure 13] Figure 13 is a meridional cross-sectional view showing an example of a pneumatic tire manufactured using the tire molding die according to this embodiment. [Figure 14] Figure 14 is a chart showing the results of an evaluation test for black residue defects. [Modes for carrying out the invention]

[0027] Embodiments of the present invention will be described below 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. In addition, some components may not be used.

[0028] (First Embodiment) A tire molding die according to the first embodiment will now be described. Figure 1 is a cross-sectional view showing an example of a tire molding die 10 according to the first embodiment. The tire molding die 10 is a mold for vulcanizing a green tire T. A pneumatic tire 100 is manufactured by vulcanizing the green tire T. In the following description, the green tire T before vulcanization will be appropriately referred to as tire T, and the pneumatic tire 100 after vulcanization will be appropriately referred to as tire 100.

[0029] Furthermore, in the following explanation, the terms mold width direction, mold circumferential direction, and mold radial direction will be used to describe the positional relationship of each part. The mold width direction is the direction parallel to the rotation axis of the tire T (tire 100) manufactured by the tire molding die 10. The mold circumferential direction is the direction of rotation of the tire T centered on the rotation axis. The mold radial direction is the direction perpendicular to the mold width direction and the mold circumferential direction, and is the radial direction with respect to the rotation axis of the tire T. The outer part of the mold radial direction refers to the part of the tire T that is away from the rotation axis in the radial direction with respect to the rotation axis. The inner part of the mold radial direction refers to the part of the tire T that is approaching the rotation axis in the radial direction with respect to the rotation axis. The mold width direction of the tire molding die 10 and the tire width direction of the tire T (tire 100) vulcanized by the tire molding die 10 are synonymous. The mold circumferential direction of the tire molding die 10 and the tire circumferential direction of the tire T vulcanized by the tire molding die 10 are synonymous. The radial direction of the tire molding die 10 and the radial direction of the tire T that is vulcanized by the tire molding die 10 are synonymous.

[0030] As shown in Figure 1, the tire molding die 10 comprises a lower side plate (one side plate) 1 for molding one side portion of the tire T, an upper side plate (the other side plate) 2 for molding the other side portion of the tire T, a lower bead ring 3 for molding one bead portion of the tire T, an upper bead ring 4 for molding the other bead portion of the tire T, and a plurality of sector molds 5 for molding the tread portion of the tire T.

[0031] A lower clamping ring 7, which clamps the lower end of the bladder 6 between itself and the lower bead ring 3, and an upper clamping ring 8 and an auxiliary ring 9, which clamp the upper end of the bladder 6, are provided in the tire molding die 10. The bladder 6 is a cylindrical member made of rubber. The bladder 6 forms the inner surface of the tire T. The upper clamping ring 8 is movable in the vertical direction. When the upper clamping ring 8 moves downward, the bladder 6 is held inside the tire T. When the upper clamping ring 8 moves upward, the bladder 6 can move from the inside to the outside of the tire T.

[0032] The tire molding die 10 is heated by a heating device. During the vulcanization of the tire T, the tire T is placed in the tire molding die 10 and positioned between the tire molding die 10 and the bladder 6. When the upper clamp ring 8 is moved downward and pressurizing gas is introduced into the bladder 6, the tire T is pressed against the tire molding die 10 by the bladder 6. With the tire T pressed against the tire molding die 10 by the bladder 6, the tire molding die 10 is heated by the heating device, and the tire T is vulcanized.

[0033] The lower side plate 1 has an inner surface 11 that forms the surface (profile surface) of the side portion of the tire T, and a recess 20 provided on the inner surface 11 that forms the white rubber layer of the tire T, which will become a white ribbon (decoration) and white letters. The white ribbon is a strip-shaped decorative part that extends in the circumferential direction of the tire T, and the white letters are decorative parts that indicate the manufacturer's name, brand name, etc.

[0034] The inner surface 11 of the tire molding die 10 corresponds to the profile surface of the vulcanized tire T (tire 100). The recess 20 forms a white rubber layer (second color rubber layer) that protrudes from the surface (profile surface) of the side portion of the tire T. The white rubber layer is covered by the black cover rubber layer (first color rubber layer) of the tire T, and this white rubber layer is not exposed. That is, in the tire T during vulcanization molding, the white rubber layer contacts the inner surface of the recess 20 via the cover rubber layer.

[0035] The vulcanized tire T is manufactured through a process in which the cover rubber layer is polished (buffed) to remove it, thereby exposing the white rubber layer formed in the recess. According to the inventor's knowledge, during tire vulcanization, the white rubber layer does not uniformly contact the inner surface of the recess 20 via the cover rubber layer, causing the formed white rubber layer to become wavy. As a result, the cover rubber layer may not be sufficiently removed even when polished. In this case, the phenomenon of the cover rubber layer remaining on the white ribbon or white lettering is called a black residue defect, and it may lead to a deterioration in the appearance of the manufactured tire 100. Therefore, by devising the shape of the recess 20, the occurrence of black residue defects is suppressed, and the manufacture of a tire 100 with a good appearance is achieved.

[0036] Next, the recess 20 will be described. Figure 2 is a cross-sectional view showing an example of a recess in the tire molding die according to the first embodiment. Figure 3 is a cross-sectional view showing another example of a recess in the tire molding die according to the first embodiment. Figure 4 is a cross-sectional view showing another example of a recess in the tire molding die according to the first embodiment. These cross-sectional views are partially enlarged cross-sectional views when the lower side plate 1 in the tire molding die 10 according to Figure 1 is cut along the diameter direction of the die. In these cross-sectional views, reference numeral 15, drawn with dashed lines, indicates the surface position of the protrusion after the white rubber layer molded in the recess 20 has been polished.

[0037] In this embodiment, the recess 20 extends along the circumferential direction of the mold and is used, for example, to form a white ribbon that extends around the entire circumference. Note that the recess 20 is not limited to a white ribbon, but may also be a part for forming a portion of white letters that extend along the circumferential direction of the mold. As shown in Figures 2 to 4, the recess 20 has a bottom surface 21 and wall surfaces 22. The wall surfaces 22 are provided on both sides of the bottom surface 21 in the radial direction of the mold. The wall surfaces 22 include a first wall surface 22A located on the outer side in the radial direction of the mold and a second wall surface 22B located on the inner side in the radial direction of the mold, facing the first wall surface 22A with a gap between them.

[0038] As shown in Figure 2, the recess 20 has a cross-sectional area of ​​the outer region 30 located radially outward from the mold's radial center CL, which is larger than the cross-sectional area of ​​the inner region 31 located radially inward from the mold's radial center CL. Here, the mold's radial center CL is defined by a perpendicular line extending from the midpoint 21C between the radially outward end 21A and the radially inward end 21B on the bottom surface 21 to the inner surface 11 (profile surface) of the tire molding die 10. The outer region 30 is the area demarcated by the bottom surface 21, the first wall surface 22A, the inner surface 11, and the mold's radial center CL of the tire molding die 10, while the inner region 31 is the area demarcated by the bottom surface 21, the second wall surface 22B, the inner surface 11, and the mold's radial center CL of the tire molding die 10.

[0039] In this embodiment, the dimensions of the recess 20 in the mold radial direction are set to be between 15 mm and 35 mm. This dimension in the mold radial direction refers to the distance between the outer end 21A and the inner end 21B in the mold radial direction on the bottom surface 21 of the recess 20. According to the inventor's findings, it has been found that setting the dimension in the mold radial direction to 20 mm or more is highly effective in suppressing the black residue defect described above. This range of dimensions in the mold radial direction is particularly effective when the object to be molded into the recess 20 is a ribbon.

[0040] Furthermore, it is preferable that the recess 20 has a dimension of 20 mm or more in the circumferential direction of the mold. This dimension in the circumferential direction of the mold refers to the continuous distance from the start end to the end of the recess 20 in the circumferential direction of the mold. If the object to be molded in the recess 20 is a letter, it will be the distance from the start end to the end of the recess 20 in the circumferential direction of the mold that constitutes a part of the letter. Also, if the object to be molded in the recess 20 is a ribbon, the dimension in the circumferential direction of the mold may be, for example, a central angle of 90° or more and 360° or less from the start end to the end of the ribbon centered on the rotation axis of the tire T.

[0041] As described above, in the recess 20, the cross-sectional area of ​​the outer region 30, located radially outward from the mold's radial center CL of the recess 20, is larger than the cross-sectional area of ​​the inner region 31, located radially inward from the mold's radial center CL. With this configuration, the cross-sectional area of ​​the outer region 30 is larger than the cross-sectional area of ​​the inner region 31 from the mold's radial center CL of the recess 20, allowing the cover rubber layer and the white rubber layer to flow smoothly into the outer region 30 of the recess 20. As a result, the white rubber layer makes uniform contact with the recess 20 of the tire molding die 10 via the cover rubber layer, reducing the waviness of the white rubber layer, and thus enabling the manufacture of a tire 100 with a good appearance.

[0042] Here, it is preferable that the cross-sectional area of ​​the outer region 30 of the recess 20 is larger than the cross-sectional area of ​​the inner region 31 located on the inside in the radial direction of the mold, over the entire circumferential direction of the mold (from the start end to the end end). However, it is sufficient that the cross-sectional area of ​​the outer region 30 is larger than the cross-sectional area of ​​the inner region 31 located on the inside in the radial direction of the mold, within a range of at least 70% to 100%, more preferably 80% to 100%, of the circumferential dimensions of the recess 20 of the mold.

[0043] Furthermore, when the cross-sectional area of ​​the outer region 30 of the recess 20 is Sh and the cross-sectional area of ​​the inner region 31 is Sl, it is preferable that the cross-sectional area Sh of the outer region 30 and the cross-sectional area Sl of the inner region 31 satisfy the relationship 1.1 ≤ Sh / Sl ≤ 1.6 and more preferably 1.2 ≤ Sh / Sl ≤ 1.4. In this configuration, the relationship between the cross-sectional area Sh of the outer region 30 and the cross-sectional area Sl of the inner region 31 satisfies the above-mentioned numerical range, allowing the rubber to flow smoothly into the outer region 30 of the recess 20. Therefore, by having the difference in cross-sectional areas between the outer region 30 and the inner region 31 within a desirable range, the rubber can flow more uniformly from the radially upper side, reducing the waviness of the rubber.

[0044] As described above, as one aspect of forming the cross-sectional area of the outer region 30 larger than the cross-sectional area of the inner region 31 with respect to the center CL in the die radial direction of the recess 20, a configuration is provided in which the depth to the bottom surface 21 in the outer region 30 of the recess 20 is formed deeper than the depth to the bottom surface 21 in the inner region 31. In the example of FIG. 2, the bottom surface 21 is formed in a curved surface shape that is convex with respect to the inner surface 11, and this bottom surface 21 gradually decreases (becomes shallower) in depth from the bottom surface 21 to the inner surface 11 (profile surface) from the end portion 21A on the outer side in the die radial direction toward the end portion 21B on the inner side in the die radial direction. Therefore, by making the bottom surface 21 into a simple shape, the recess 20 in which the cross-sectional area of the outer region 30 is larger than the cross-sectional area of the inner region 31 can be easily formed.

[0045] Further, when the maximum depth to the bottom surface 21 in the outer region 30 of the recess 20 is Dh and the maximum depth to the bottom surface 21 in the inner region 31 is Dl, the maximum depth Dh of the outer region 30 and the maximum depth Dl of the inner region 31 are each 3 mm or more and 6 mm or less, and Dl < Dh is satisfied. In the example of FIG. 2, the end portion 21A on the outer side in the die radial direction is the position where the maximum depth Dh from the inner surface 11 to the bottom surface 21 in the outer region 30 is reached, and the midpoint 21C from the end portion 21A on the outer side in the die radial direction to the end portion 21B on the inner side in the die radial direction is the position where the maximum depth Dl from the inner surface 11 to the bottom surface 21 in the inner region 31 is reached. In this configuration, by satisfying the above numerical ranges for the maximum depth Dh of the outer region 30 and the maximum depth Dl of the inner region 31, an appropriate amount of the white rubber layer formed by the recess 20 can be obtained, and an increase in cost and the occurrence of black residue defects due to insufficient white rubber can be suppressed.

[0046] Note that the shape of the bottom surface is not limited to that shown in Figure 2. As shown in Figure 3, the bottom surface 121 may be formed in a flat shape, or as shown in Figure 4, the bottom surface 221 may be formed in a curved shape that combines a convex shape and a concave shape relative to the inner surface 11. In the example in Figure 3, the bottom surface 121 is formed with a uniformly shallow (small) depth from the inner surface 11 to the bottom surface 21, from the outer end 121A in the radial direction of the mold to the inner end 121B in the radial direction of the mold. In this case, the outer end 121A in the radial direction of the mold is the position where the maximum depth Dh from the inner surface 11 to the bottom surface 121 in the outer region 30 is reached, and the midpoint 121C from the outer end 121A in the radial direction of the mold to the inner end 121B in the radial direction of the mold is the position where the maximum depth Dl from the inner surface 11 to the bottom surface 121 in the inner region 31 is reached. This configuration allows for a simple shape for the bottom surface 121, and makes it easy to form recesses 20 with precisely defined cross-sectional areas for the outer region 30 and inner region 31.

[0047] Furthermore, in the example shown in Figure 4, the bottom surface 221 is formed as a curved surface that is convex relative to the inner surface 11 in the range from the outer end 221A in the radial direction of the mold to the midpoint 221C between the end 221A and the inner end 221B in the radial direction of the mold, and as a curved surface that is concave relative to the inner surface 11 in the range from the midpoint 221C to the inner end 221B in the radial direction of the mold. In this case, the vertex 221D between the outer end 221A in the radial direction of the mold and the midpoint 221C is the position of the maximum depth Dh from the inner surface 11 to the bottom surface 221 in the outer region 30, and the midpoint 221C or the inner end 221B in the radial direction of the mold is the position of the maximum depth Dl from the inner surface 11 to the bottom surface 221 in the inner region 31. With this configuration, a recess 20 can be easily formed with a large cross-sectional area ratio (Sh / Sl) between the outer region 30 and the inner region 31.

[0048] Next, the wall surface 22 of the recess 20 will be described. Figure 5 is a cross-sectional view showing an example of the outer wall surface in the mold radial direction in the recess of the tire molding die according to the first embodiment. Figure 6 is a cross-sectional view showing an example of the inner wall surface in the mold radial direction in the recess of the tire molding die according to the first embodiment. As shown in Figures 5 and 6, the first wall surface 22A and the second wall surface 22B of the recess 20 are inclined to become wider from the bottom surface 21 toward the inner surface 11. Specifically, in the recess 20, the wall angle Y1 of the first wall surface 22A on the outer side in the mold radial direction with respect to the perpendicular 33 from the outer end 21A on the outer side in the mold radial direction to the inner surface 11 (profile surface) is formed to be larger than the wall angle Y2 of the second wall surface 22B on the inner side in the mold radial direction with respect to the perpendicular 34 from the inner end 21B on the inner surface 11 toward the inner surface 11. If the wall surface is curved, for example, the wall angles Y1 and Y2 can be measured by drawing tangents to the wall surface from each end and measuring the angle between these tangents and the perpendicular from the end to the inner surface. According to the above configuration, by making the wall angle Y1 of the first wall surface 22A larger than the wall angle Y2 of the second wall surface 22B, the cross-sectional area of ​​the outer region 30 of the recess 20 is made larger than the cross-sectional area of ​​the inner region 31. Therefore, since the rubber flows well into the outer region 30 of the recess 20, the white rubber layer comes into uniform contact with the recess 20 of the tire molding die 10, reducing the waviness of the white rubber layer, and thus enabling the manufacture of a tire 100 with a good appearance.

[0049] More specifically, the wall angle Y1 of the first wall surface 22A is set to 10° or more and 30° or less, and more preferably to 20° or more and 25° or less. This configuration allows for an increase in the cross-sectional area of ​​the outer region 30. As a result, the rubber flows well into the outer region 30, and the white rubber layer makes uniform contact with the recess 20 of the tire molding die 10, reducing the waviness of the white rubber layer, thus enabling the manufacture of a tire 100 with a good appearance.

[0050] Furthermore, the wall angle Y2 of the second wall surface 22B is set to 0° or more and 10° or less, and more preferably to 5° or more and 7° or less. With this configuration, the rubber flows well from the inner region 31 to the outer region 30, so that the white rubber layer comes into uniform contact with the recess 20 of the tire molding die 10, thereby reducing the waviness of the white rubber layer and enabling the manufacture of a tire 100 with a good appearance.

[0051] Furthermore, as shown in Figures 2 to 4, the tire molding die 10 is provided with bend grooves 13 extending in the circumferential direction of the die on the inner surfaces 11 on both sides of the recess 20 in the radial direction of the die. These bend grooves 13 serve as passages for discharging residual gas from inside the tire molding die 10 to the outside.

[0052] Next, an example of a method for manufacturing a tire produced using the tire molding die according to this embodiment will be described. Figure 7 is a cross-sectional view showing an example of a protruding portion of a pneumatic tire molded using the tire molding die according to the first embodiment before polishing. Figure 8 is a cross-sectional view showing an example of a protruding portion of a pneumatic tire molded using the tire molding die according to the first embodiment after polishing.

[0053] The method for manufacturing the tire 100 includes a vulcanization step of manufacturing the tire 100 by vulcanizing the tire T using a tire molding die 10, a polishing step of polishing the cover rubber layer that covers the white rubber layer of the tire 100 to expose the white rubber layer, and a step of performing an appearance inspection of the tire 100.

[0054] A tire T, in which a white rubber layer forming a white ribbon is embedded in the side portion, is placed into a tire molding die 10, and the tire T is vulcanized. In this case, the surface of the side portion of the tire T is formed on the inner surface 11 of the lower side plate 1. The white rubber layer is covered by a cover rubber layer, and the white rubber layer, together with the cover rubber layer, is formed in a recess 20 provided in the lower side plate 1.

[0055] As the tire T is vulcanized using the tire molding die 10, a protrusion 70 formed by the recess 20 is created on the side of the tire 100, as shown in Figure 7. The protrusion 70 includes a white rubber layer 72 and a black cover rubber layer 71 that covers the white rubber layer 72.

[0056] The surface of the protrusion 70 is polished (e.g., buffed) up to position 15, which removes the cover rubber layer 71 that covers the white rubber layer 72. With the removal of this cover rubber layer 71, the white rubber layer 72 is exposed on the surface of the protrusion 70. As a result, a white ribbon (or white letters) is formed on the side of the tire 100. After this white ribbon is formed, the tire 100 is visually inspected.

[0057] (Second Embodiment) Next, a second embodiment will be described. In the following description, the same reference numerals will be used for components identical to those in the above-described embodiment, and their descriptions will be simplified or omitted.

[0058] Figure 9 is a cross-sectional view showing an example of a recess in a tire molding die according to the second embodiment. Figure 10 is a cross-sectional view showing another example of a recess in a tire molding die according to the second embodiment. Figure 11 is a cross-sectional view showing another example of a recess in a tire molding die according to the second embodiment. In this second embodiment, as another configuration in which the cross-sectional area of ​​the outer region 30 is made larger than the cross-sectional area of ​​the inner region 31 with respect to the mold radial center CL of the recess 20, a projection is provided on at least a part of the bottom surface of the recess 20 that protrudes inward (towards the inner surface 11), and the cross-sectional area of ​​the projection in the inner region 31 is made larger than the cross-sectional area of ​​the projection in the outer region 30.

[0059] As shown in Figure 9, the recess 20 has a projection 40 that protrudes toward the inner surface 11 at the center of the bottom surface 321. That is, the cross-sectional area of ​​the recess 20 is reduced because the bottom surface 321 partially protrudes inward into the recess 20. In the example of Figure 9, the projection 40 is provided in a stepped manner in the radial direction of the mold, straddling the mold radial center CL, and the depth of the bottom surface 321 in the inner region 31 is formed to be shallower than the depth of the bottom surface 321 in the outer region 30. Therefore, the cross-sectional area of ​​the outer region 30 of the recess 20 is formed to be larger than the cross-sectional area of ​​the inner region 31 with respect to the mold radial center CL.

[0060] The shape of the protrusion 40 is not limited to a stepped shape. For example, as shown in Figure 10, the protrusion 40 may be formed in a triangular shape, with the height of the triangle increasing from the outer region 30 to the inner region 31, i.e., the depth of the bottom surface 321 becoming shallower. Alternatively, as shown in Figure 11, the length of the protrusion 40 in the inner region 31 in the mold circumferential direction may be made larger than that of the outer region 30. Furthermore, the bottom surface 321 of the protrusion 40 in the inner region 31 may be formed as a curved surface that is convex relative to the inner surface 11, while the bottom surface 321 of the protrusion 40 in the outer region 30 may be formed as a curved surface that is concave relative to the inner surface 11. With such a configuration, the recess 20 can be formed so that the cross-sectional area of ​​the outer region 30 is larger than that of the inner region 31 with respect to the mold radial center CL.

[0061] The projection 40 described above is preferably formed over the entire circumferential area of ​​the mold (from the start end to the end end), but it is sufficient if it is formed in an area of ​​at least 70% to 100%, more preferably 80% to 100%, of the circumferential dimension of the recess 20. In this embodiment, an example has been described in which the projection 40 is formed in both the outer region 30 and the inner region 31, straddling the radial center CL of the mold, but the projection 40 may also be provided only in the inner region 31.

[0062] Furthermore, in this embodiment, the recess 20 is provided with a bend groove 13 extending in the circumferential direction of the mold on the bottom surface 321, as shown in Figure 12. This bend groove 13 is formed on the bottom surface 321 so as to be convex relative to the inner surface 11 and serves as a passage for discharging residual gas from inside the tire molding die 10 to the outside. Therefore, during vulcanization, residual gas is efficiently guided from the shallow side to the deep side of the recess 20 and sufficiently discharged from between the tire T and the tire molding die 10. In addition, the cover rubber layer 71 and the white rubber layer 72 flow well into the outer region 30 of the recess 20. As a result, the white rubber layer makes uniform contact with the recess 20 of the tire molding die 10 via the cover rubber layer, reducing the waviness of the white rubber layer, thereby suppressing the occurrence of black residue defects and ultimately enabling the manufacture of a tire 100 with a good appearance.

[0063] In the example shown in Figure 12, the recess 20 is configured to have the projection 40, and a bend groove 13 is provided on the bottom surface 321 of the region corresponding to the projection 40. However, the configuration is not limited to this, and for example, the bend groove 13 may be provided on the bottom surface 21 (121, 221) of the recess 20 shown in Figures 2 to 4.

[0064] Figure 13 is a meridional cross-sectional view showing an example of a tire 100 according to this embodiment, manufactured by the manufacturing method described above. As shown in Figure 13, the tire 100 comprises a carcass 102, a belt layer 103, a belt cover 104, a bead portion 105, a tread portion 106, a side portion 107, and a protrusion 70 provided on the side portion 107. The tread portion 106 includes tread rubber 108. The side portion 107 includes side rubber 109.

[0065] The carcass 102 is a structural member that forms the framework of the tire 100. The carcass 102 includes carcass cords and functions as a pressure vessel when the tire 100 is filled with air.

[0066] The bead portion 105 is a reinforcing member that supports the carcass 102. The bead portion 105 has a bead core 151 and a bead filler 152. The bead portion 105 is positioned on both sides of the carcass 102 in the tire width direction and supports both ends of the carcass 102. The carcass 102 is folded over at the bead core 151 of the bead portion 105. The bead portion 105 secures the tire 100 to the rim.

[0067] The carcass 102 has a carcass body and a carcass folded portion formed by folding over the bead core 151. The carcass folded portion is the part that is positioned outward in the tire width direction from the carcass body as a result of the carcass 102 being folded over by the bead core 151. The bead core 151 is a member in which bead wire is wound in a ring shape. The bead wire is steel wire. The bead filler 152 is a rubber material placed in the space between the carcass body formed by the carcass 102 being folded over by the bead core 151 and the carcass folded portion.

[0068] The belt layer 103 is a strength member that maintains the shape of the tire 100. The belt layer 103 is positioned between the carcass 102 and the tread rubber 108. The belt layer 103 includes belt cords and rubber covering the belt cords. The belt layer 103 includes a first belt ply 131 and a second belt ply 132. The first belt ply 131 and the second belt ply 132 are laminated such that the belt cords of the first belt ply 131 and the belt cords of the second belt ply 132 intersect.

[0069] The belt cover 104 is a structural member that protects and reinforces the belt layer 103. The belt cover 104 is positioned outside the belt layer 103 with respect to the rotation axis of the tire 100. The belt cover 104 includes a cover cord and rubber covering the cover cord.

[0070] The tread rubber 108 protects the carcass 102. The tread portion 106 includes the tread rubber 108, which is provided with a plurality of grooves. The tread portion 106 includes land portions arranged between the grooves, and the land portions have a contact surface (tread) that contacts the road surface. The grooves include a plurality of main grooves arranged in the circumferential direction of the tire and lug grooves, at least a portion of which are arranged in the width direction of the tire.

[0071] The tread portion 106 includes a center portion containing the center CL1 in the tire width direction, and shoulder portions provided on both sides of the center portion in the tire width direction. Main grooves are provided in the center portion and the shoulder portions, respectively. Lug grooves are also provided in the center portion and the shoulder portions, respectively.

[0072] The side rubber 109 protects the carcass 102. The side portion 107 includes the side rubber 109 and is positioned on both sides of the tread portion 106 in the tire width direction.

[0073] The surface of the side portion 107 includes the surface of the side rubber 109. The protruding portion 70 protrudes outward from the surface of the side portion 107 in the tire width direction.

[0074] The protrusion 70 is provided on one side portion 107 of the tire width direction center CL1, but not on the other side portion 107. The protrusion 70 includes a white ribbon formed in an annular shape. The protrusion 70 does not have to be a ribbon; it may represent letters, symbols, or figures.

[0075] The side rubber 109 is black rubber. The side rubber 109 includes, for example, a diene-based rubber material reinforced with carbon. The white rubber layer 72 includes a diene-based rubber material reinforced with, for example, a white filler such as titanium dioxide or clay. In this embodiment, the stiffness of the white rubber layer 72 is less than the stiffness of the side rubber 109.

[0076] As described above, the tire molding die 10 according to this embodiment includes a lower side plate 1 for molding the side portion of the tire 100, and a recess 20 provided on the lower side plate 1, having a bottom surface 21 and a wall surface 22 that contact the cover rubber layer 71 of the tire 100, and for molding the white rubber layer 72 of the tire 100 that protrudes from the side portion and is covered by the cover rubber layer 71. The recess 20 has an outer region 30 located on the outer side in the radial direction of the mold with respect to the mold radial center CL of the recess 20, and the cross-sectional area of ​​the outer region 30 located on the inner side in the radial direction of the mold is larger than the cross-sectional area of ​​the inner region 31. With this configuration, the cross-sectional area of ​​the outer region 30 of the recess 20 is larger than the cross-sectional area of ​​the inner region 31, allowing the cover rubber layer 71 and the white rubber layer 72 to flow well into the outer region 30 of the recess 20. Therefore, the white rubber layer 72 comes into uniform contact with the recess 20 of the tire molding die 10 via the cover rubber layer 71, which reduces the waviness of the white rubber layer 72. As a result, the occurrence of black residue defects is suppressed, and a tire 100 with a good appearance can be manufactured.

[0077] Furthermore, according to this embodiment, when the cross-sectional area of ​​the outer region 30 is Sh and the cross-sectional area of ​​the inner region 31 is Sl, the relationship between the cross-sectional area of ​​the outer region 30 and the cross-sectional area of ​​the inner region 31 satisfies 1.1 ≤ Sh / Sl. Therefore, the cross-sectional area Sh of the outer region 30 can be made even larger than the cross-sectional area Sl of the inner region 31, and the waviness of the white rubber layer 72 is reduced, so the occurrence of black residue defects is suppressed and a tire 100 with a good appearance can be manufactured.

[0078] Furthermore, according to this embodiment, since the depth of the recess 20 to the bottom surface 21 in the outer region 30 is greater than the depth of the recess 20 to the bottom surface 21 in the inner region 31, a recess 20 in which the cross-sectional area of ​​the outer region 30 is larger than the cross-sectional area of ​​the inner region 31 can be created with a simple structure.

[0079] Further, according to the present embodiment, for the concave portion 20, when the maximum depth to the bottom surface 21 in the outer region 30 is Dh and the maximum depth to the bottom surface 21 in the inner region 31 is Dl, the maximum depth of the outer region 30 and the maximum depth of the inner region 31 are each 3 mm or more and 6 mm or less, and Dl < Dh is satisfied. Therefore, an appropriate amount of the white rubber layer 72 formed by the concave portion 20 can be obtained, and an increase in cost and the occurrence of black residue defects due to rubber shortage in the white rubber layer 72 can be suppressed.

[0080] Further, according to the present embodiment, the concave portion 20 has a protrusion 40 protruding inward on at least a part of the bottom surface 321, and the cross-sectional area of the protrusion 40 in the inner region 31 is larger than the cross-sectional area of the protrusion in the outer region 30. Therefore, the concave portion 20 in which the cross-sectional area of the outer region 30 is larger than the cross-sectional area of the inner region 31 can be created with a simple configuration.

[0081] Further, according to the present embodiment, for the concave portion 20, the wall angle Y1 of the first wall surface 22A on the outer side in the mold radial direction with respect to the perpendicular line 33 from the end portion 21A on the outer side in the mold radial direction to the inner surface 11 of the tire is larger than the wall angle Y2 of the second wall surface 22B on the inner side in the mold radial direction with respect to the perpendicular line 34 from the end portion 21B on the inner side in the mold radial direction to the inner surface 11 of the tire. Therefore, the concave portion 20 in which the cross-sectional area of the outer region 30 is larger than the cross-sectional area of the inner region 31 can be created with a simple configuration.

[0082] Further, according to the present embodiment, for the concave portion 20, the wall angle Y1 of the first wall surface 22A on the outer side in the mold radial direction with respect to the perpendicular line 33 from the end portion 21A on the outer side in the mold radial direction to the inner surface 11 of the tire is 10° or more and 30° or less. According to this configuration, rubber flows well in the outer region 30, and the white rubber layer 72 hits the concave portion 20 of the tire molding die 10 uniformly through the cover rubber layer 71, so that the undulation of the white rubber layer 72 is reduced, the occurrence of black residue defects is suppressed, and a tire 100 with a good appearance can be manufactured.

[0083] Furthermore, according to this embodiment, the wall angle Y2 of the second wall surface 22B on the inner side of the mold in the radial direction with respect to the perpendicular 34 from the end 21B on the inner side of the mold in the radial direction to the inner surface 11 of the tire is 0° or more and 10° or less. With this configuration, the rubber flows smoothly from the inner region 31 to the outer region 30, and the white rubber layer 72 comes into uniform contact with the recess 20 of the tire molding die 10 via the cover rubber layer 71, thereby reducing the waviness of the white rubber layer 72. This suppresses the occurrence of black residue defects and makes it possible to manufacture a tire 100 with a good appearance.

[0084] Furthermore, according to this embodiment, the recess 20 is provided with at least one bend groove 13 extending in the circumferential direction of the mold on the bottom surface 321. During vulcanization, the bend groove 13 efficiently guides residual gas from the shallower side to the deeper side of the recess 20, and it is sufficiently discharged from between the tire 100 and the tire molding die 10. As a result, the white rubber layer 72 makes uniform contact with the recess 20 of the tire molding die 10 via the cover rubber layer 71, reducing the waviness of the white rubber layer 72. This suppresses the occurrence of black residue defects, and consequently, makes it possible to manufacture a tire 100 with a good appearance.

[0085] Furthermore, according to this embodiment, the recess 20 extends continuously in at least a portion of the circumferential direction of the mold to form a ribbon or part of a character using the white rubber layer 72, thereby improving the molding accuracy of the white ribbon or white character.

[0086] (Examples) A tire T was vulcanized using a tire molding die, the cover rubber layer 71 of the vulcanized tire 100 was polished, and the appearance of the polished tire 100 was inspected to evaluate the level of black residue defects.

[0087] The tire size of the manufactured tire 100 is 185 / 75R14 89S. An automatic buffing device was used to polish the surface of the protrusion 70 on the side portion 107 of the vulcanized tire 100 to a predetermined position 15. After polishing, the tire 100 was visually inspected to see if any black residue defects had occurred, and the failure rate (defect rate) was measured. 400 tires 100 were manufactured using multiple tire molding dies with different recess structures 20, and each of these multiple tires 100 was evaluated. The failure rate was calculated from the number of tires that exhibited black residue defects that did not meet the inspection standards.

[0088] Figure 14 is a chart showing the results of an evaluation test for black residue defects. In the table shown in Figure 14, the tire molding die according to Conventional Example 1 has a recess 20 for molding the white rubber layer 72, but the cross-sectional areas of the outer region 30 and the inner region 31 of the recess 20 are the same. In the Comparative Example, the cross-sectional area of ​​the outer region 30 of the recess 20 is smaller than that of the inner region 31. The tire molding dies according to Examples 1 to 13 are tire molding dies that fall within the technical scope of the invention of this application. In the tire molding dies according to Examples 1 to 13, the cross-sectional area of ​​the outer region 30 of the recess 20 is larger than that of the inner region 31.

[0089] In Conventional Example 1, the failure rate is set at 4%, and a failure rate of 2% or less indicates a high percentage of good products.

[0090] As shown in Examples 1 to 13, it was confirmed that the failure rate decreased and the yield rate increased by forming the outer region 30 of the recess 20 to have a larger cross-sectional area than the inner region 31. The yield rate could be increased by adjusting the maximum depth of the outer region 30 and the inner region 31 of the recess 20, the wall angle of the wall surfaces 22 located on both sides of the mold in the radial direction of the recess 20, the dimensions of the recess 20 in the mold in the radial direction, and the presence or absence of the bend groove 13.

[0091] This disclosure encompasses the following inventions:

[0092] Invention [1] A side plate that forms the side of the tire, It is provided on the side plate, has a bottom surface and a wall surface that contact the first color rubber layer of the tire, and includes a recess for forming a second color rubber layer of the tire that protrudes from the side portion and is covered with the first color rubber layer. The recess is a tire molding die in which, with respect to the center of the die in the radial direction of the recess, the cross-sectional area of the outer region located on the outer side in the radial direction of the die is larger than the cross-sectional area of the inner region located on the inner side in the radial direction of the die.

[0093] Invention [2] When the cross-sectional area of the outer region of the recess is Sh and the cross-sectional area of the inner region is Sl, The tire molding die according to Invention [1], wherein the cross-sectional area of the outer region and the cross-sectional area of the inner region satisfy the relationship of 1.1 ≦ Sh / Sl.

[0094] Invention [3] The tire molding die according to Invention [1] or Invention [2], wherein the depth of the bottom surface in the outer region of the recess is deeper than the depth of the bottom surface in the inner region.

[0095] Invention [4] When the maximum depth of the bottom surface in the outer region of the recess is Dh and the maximum depth of the bottom surface in the inner region is Dl, the maximum depth of the outer region and the maximum depth of the inner region are each 3 mm or more and 6 mm or less, and satisfy Dl < Dh. The tire molding die according to any one of Inventions [1] to [3].

[0096] Invention [5] The tire molding die according to any one of Inventions [1] to [4], wherein the recess has a protrusion protruding inward of the recess on at least a part of the bottom surface, and the cross-sectional area of the protrusion in the inner region is larger than the cross-sectional area of the protrusion in the outer region.

[0097] ] Invention [6] A tire molding die according to any one of inventions [1] to [5], wherein the recess is such that the wall angle of the wall surface on the radially outer side of the mold with respect to a perpendicular from the radially outer end of the mold to the profile surface of the tire is greater than the wall angle of the wall surface on the radially inner side of the mold with respect to a perpendicular from the radially inner end of the mold to the profile surface of the tire.

[0098] invention [7] The tire molding die according to any one of inventions [1] to [6], wherein the recess is such that the wall angle of the wall surface on the radially outer side of the mold with respect to a perpendicular from the radially outer end of the mold to the profile surface of the tire is 10° or more and 30° or less.

[0099] invention [8] The tire molding die according to any one of inventions [1] to [7], wherein the recess is such that the wall angle of the wall surface on the inner side of the mold in the radial direction with respect to a perpendicular from the inner end of the mold in the radial direction to the profile surface of the tire is 0° or more and 10° or less.

[0100] invention[9] The tire molding die according to any one of inventions [1] to [8], wherein the recess comprises at least one bend groove extending in the circumferential direction of the mold on the bottom surface.

[0101] Invention

[10] The tire molding die according to any one of the inventions [1] to [9], wherein the recess extends continuously in at least a portion of the circumferential direction of the mold to form a ribbon or part of a character of the second colored rubber layer. [Explanation of Symbols]

[0102] 1. Lower side plate (side plate) 10 Tire molding dies 11. Inner surface (profile surface) 13 Bend Grooves 20 recesses 21,121,221,321 base 21A, 21B, 121A, 121B, 221A, 221B End 21C,121C,221C midpoint 22 Wall surface 22A First Wall 22B 2nd wall 30 outer area 31 Inner area 33,34 Perpendicular lines 40 Protrusion 70 Protrusion 71 Cover rubber layer (first color rubber layer) 72 White rubber layer (second colored rubber layer) 100 Tires (Pneumatic Tires) Dh,Dl Maximum depth Sh,Sl cross-sectional area T-Tire (Green Tire) Y1, Y2 Wall angle

Claims

1. A side plate that forms the side of the tire, The side plate is provided with a bottom surface and a wall surface that contact the first colored rubber layer of the tire, and includes a recess that protrudes from the side portion and forms the second colored rubber layer of the tire which is covered by the first colored rubber layer, The aforementioned recess is a tire molding die in which the cross-sectional area of ​​the outer region located radially outward of the mold with respect to the radial center of the mold is larger than the cross-sectional area of ​​the inner region located radially inward of the mold.

2. The recess is defined as follows, where Sh is the cross-sectional area of ​​the outer region and Sl is the cross-sectional area of ​​the inner region. The tire molding die according to claim 1, wherein the cross-sectional area of ​​the outer region and the cross-sectional area of ​​the inner region satisfy the relationship 1.1 ≤ Sh / Sl.

3. The tire molding die according to claim 1 or 2, wherein the depth of the recess to the bottom surface in the outer region is greater than the depth to the bottom surface in the inner region.

4. The tire molding die according to claim 1 or 2, wherein, when the maximum depth to the bottom surface in the outer region is Dh and the maximum depth to the bottom surface in the inner region is Dl, the maximum depth of the outer region and the maximum depth of the inner region are each 3 mm or more and 6 mm or less, and Dl < Dh.

5. The tire molding die according to claim 1 or 2, wherein the recess has a projection that protrudes inward from at least a portion of the bottom surface of the recess, and the cross-sectional area of ​​the projection in the inner region is greater than the cross-sectional area of ​​the projection in the outer region.

6. The tire molding die according to claim 1 or 2, wherein the wall angle of the wall surface on the radially outer side of the mold with respect to a perpendicular from the radially outer end of the mold to the profile surface of the tire is greater than the wall angle of the wall surface on the radially inner side of the mold with respect to a perpendicular from the radially inner end of the mold to the profile surface of the tire.

7. The tire molding die according to claim 1 or 2, wherein the recess is such that the wall angle of the wall surface on the radially outer side of the mold with respect to a perpendicular line from the radially outer end of the mold to the profile surface of the tire is 10° or more and 30° or less.

8. The tire molding die according to claim 1 or 2, wherein the recess is such that the wall angle of the wall surface on the inner side of the mold in the radial direction is 0° or more and 10° or less with respect to a perpendicular line from the inner end of the mold in the radial direction to the profile surface of the tire.

9. The tire molding die according to claim 1 or 2, wherein the recess comprises at least one bend groove extending in the circumferential direction of the mold on the bottom surface.

10. The tire molding die according to claim 1 or 2, wherein the recess extends continuously in at least a portion of the circumferential direction of the mold to form a ribbon or part of a character using the second colored rubber layer.

Images