Tire molding die, method for producing tire and tire using the same

Abstract

To provide a tire molding die capable of improving tire appearance and air resistance around a tire while maintaining good exhaust performance and to provide a method for producing a tire and a tire using the same.SOLUTION: There is provided a tire molding die for forming a tire having a display object 10 comprising a recess 11 on the outer surface of a sidewall part 2, wherein a side plate 21 for forming the sidewall part 2 comprises a protrusion 11' corresponding to the recess 11, a flat part 12' formed adjacently to the protrusion 11' and an air vent slit 40 formed to open into the flat part 12' around the protrusion 11'.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a tire molding mold for molding tires, a tire manufacturing method using the same, and tires; and more particularly, to a tire molding mold for molding tires that can suppress defects in tire appearance and reduce air resistance around the tire, a tire manufacturing method using the same, and tires. [Background technology]

[0002] The outer surface of a tire's sidewall may be provided with markings to display the manufacturer's name, brand name, etc. Such markings may include recesses recessed from the outer surface of the sidewall, with letters, figures, or symbols depicted in the shape of the recesses (see, for example, Patent Document 1). The side plates of a tire mold for manufacturing such tires are provided with protrusions corresponding to the recesses. Because these protrusions are the first to come into contact with the uncured tire, air is less likely to accumulate inside the letters (recesses) on the tire. However, the flat areas around the protrusions (the sidewall surface surrounding the letters on the tire) tend to be more susceptible to vulcanization defects than the aforementioned letters (recesses). For this reason, conventional tire molds often have vent holes (thin exhaust holes) in the flat areas around the protrusions. However, when exhausting air through the vent holes, rubber may flow into the vent holes, potentially causing spews, or whisker-like protrusions, on the surface of the protrusions. Such spew is removed before the finished tire is shipped, but even after the spew is removed, the base of the spew remains as a tiny cylindrical protrusion, and there is a risk that traces of the spew (cut marks) will remain on the surface of the sidewall. The presence of such cut marks will deteriorate the tire's appearance, and there is also concern that the minute irregularities on the tire surface caused by the cut marks will affect the air resistance around the tire. Therefore, there is a need for measures to efficiently vent air during vulcanization without affecting the tire's appearance or the air resistance around the tire. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-006531 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a tire molding mold that makes it possible to improve the appearance of a tire after vulcanization and the air resistance around the tire while maintaining good exhaust performance, a tire manufacturing method using the same, and a tire. [Means for solving the problem]

[0005] In order to achieve the above-mentioned object, the tire molding mold of the present invention is a tire molding mold for molding a tire having indicia on the outer surface of a sidewall portion, the indicia depicting letters, figures or symbols by the shape of a recess recessed from the outer surface of the sidewall portion, the tire molding mold having a side plate for molding the sidewall portion, the side plate having a protrusion corresponding to the recess, a flat portion formed adjacent to the protrusion, and an air vent slit formed around the protrusion so as to open into the flat portion.

[0006] The tire manufacturing method of the present invention for achieving the above object is a tire manufacturing method using the tire molding mold, characterized in that an unvulcanized tire is placed into the tire molding mold, and the unvulcanized tire is vulcanized in the tire molding mold while air is removed through a slit.

[0007] In addition, the tire of the present invention for achieving the above object is a tire manufactured by the above tire manufacturing method, and is characterized in that it has traces of slits in at least a part of the sidewall portion around the recess that constitutes the indicia. [Effects of the Invention]

[0008] The inventors of the present invention conducted extensive research into venting methods for tire molds and discovered that by providing a slit-shaped vent mechanism instead of conventional vent holes, it is possible to prevent poor appearance and reduce air resistance around the tire while maintaining good venting performance. Specifically, with conventional vent holes, rubber may flow into the vent holes, causing spew, and even after the spew is removed, there is a possibility of a cut mark (the base of the spew remaining as a tiny cylindrical protrusion). However, because the slit is a tiny gap, rubber is less likely to flow into it. Even if a mark remains due to rubber that has flowed into the slit, it is only a very thin, linear mark, so the tire appearance is not impaired and air resistance around the tire is not adversely affected. The present invention is based on this discovery, and by providing air-venting slits as described above, particularly in the flat areas around the protrusions, it is possible to prevent poor appearance and reduce air resistance around the tire while maintaining excellent venting performance in the flat areas prone to vulcanization failure.

[0009] The tire manufacturing method of the present invention uses the tire mold of the present invention described above, and therefore air remaining in the mold during vulcanization can be efficiently vented to the outside of the mold through the slits. At this time, since the slits are minute gaps as described above, rubber does not substantially flow into them, and even if traces of the slits remain due to the rubber that has flowed into them, only fine linear traces remain in the tire, so that if traces of the exhaust system remain, they do not detract from the tire's appearance even on flat areas where such traces are more noticeable, and air resistance around the tire can be reduced.

[0010] Furthermore, since the tire manufactured using the tire molding mold of the present invention (tire of the present invention) is manufactured by the manufacturing method of the present invention described above, substantially no traces of the air vent slits remain, as described above, preventing poor appearance and reducing air resistance around the tire.

[0011] In the tire mold of the present invention, the slit width is preferably 0.01 mm to 0.5 mm. By making the slit width sufficiently thin in this way, it is possible to reliably prevent the inflow of rubber while maintaining exhaust performance, which is advantageous for preventing poor appearance and reducing air resistance. In the present invention, the "slit width" refers to the length measured along the short side of the slit.

[0012] In the tire molding mold of the present invention, when a plurality of protrusions form a series of protrusion rows, the maximum tire radial dimension of a protrusion included in the protrusion row is defined as character height Ch, the maximum tire circumferential dimension of a protrusion included in the protrusion row is defined as character width Cw, and the larger of character height Ch and character width Cw is defined as maximum dimension A, and the peripheral region is defined as an area surrounded by a pair of imaginary lines extending in the tire radial direction at a position spaced the maximum dimension A outward from the tire circumferential center position of each of the protrusions located at both ends of the protrusion row in the tire circumferential direction, and a pair of imaginary lines extending in the tire circumferential direction at positions spaced the maximum dimension A on both sides of the tire radial center position of the protrusion having maximum dimension A, it is preferable that the slits be located within the peripheral region. This allows the slits to be located in appropriate positions close to the protrusions (recesses in the tire), which is advantageous for preventing poor appearance and reducing air resistance around the tire while exhibiting excellent exhaust performance.

[0013] In this case, it is preferable that the total length of the slits in the tire circumferential direction is 30% or more of the length of the peripheral region in the tire circumferential direction. Also, it is preferable that the total length of the slits in the tire radial direction is 30% or more of the length of the peripheral region in the tire radial direction. By providing the slits with a sufficient length in this way, it is possible to achieve good exhaust performance through the slits.

[0014] The tire mold of the present invention may be designed so that a slit is provided in the flat portion sandwiched between the plurality of convex portions included in the convex portion row. Because the portion sandwiched between the convex portions tends to be prone to air trapping, providing a slit in this portion is advantageous for improving exhaust performance.

[0015] The tire mold of the present invention can also be configured to include a spare piece having at least one slit formed therein and a hole formed in the side plate into which the spare piece is inserted. This configuration makes it easier to clean the inside of the slit when cleaning the mold after vulcanization, thereby improving productivity. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a meridian cross-sectional view showing an example of a tire according to an embodiment of the present invention. [Figure 2] 1 is an explanatory diagram showing an example of a sidewall portion of a tire according to an embodiment of the present invention. FIG. [Figure 3] 1 is an explanatory diagram showing an example of a tire vulcanizing apparatus including a tire molding mold of the present invention. FIG. [Figure 4] FIG. 2 is an explanatory diagram showing an enlarged view of a main part of a tire molding mold according to an embodiment of the present invention. [Figure 5] FIG. 2 is an explanatory diagram showing an enlarged view of a main part of a tire molding mold according to an embodiment of the present invention. [Figure 6] FIG. 4 is an explanatory view showing an enlarged view of a main part of a tire mold according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0017] The configuration of the present invention will be described in detail below with reference to the accompanying drawings.

[0018] FIG. 1 shows an example of a tire manufactured using the tire vulcanization mold of the present invention (hereinafter referred to as the "tire of the present invention"). The tire of FIG. 1 is a pneumatic tire that includes a tread portion 1 that contacts the road surface, a pair of sidewall portions 2 arranged on both sides of the tread portion 1, and a pair of bead portions 3 arranged radially inward of the sidewall portions 2. In FIG. 1, the symbol CL indicates the tire equator. Although not depicted in FIG. 1 because it is a meridian cross-section, the tread portion 1, sidewall portions 2, and bead portions 3 each extend circumferentially in the tire direction and form an annular shape, thereby forming the basic toroidal structure of a pneumatic tire. The following explanation using FIG. 1 will be based essentially on the meridian cross-section shown, but each tire component also extends circumferentially in the tire direction and forms an annular shape.

[0019] In the tire of FIG. 1, a carcass layer 4 is installed between a pair of left and right bead portions 3. The carcass layer 4 includes a plurality of reinforcing cords extending in the tire radial direction and is folded back from the inner side to the outer side in the tire width direction around a bead core 5 arranged in each bead portion 3. A bead filler 6 is arranged on the outer periphery of the bead core 5, and this bead filler 6 is wrapped by the main portion and the folded back portion of the carcass layer 4. Meanwhile, a plurality of belt layers 7 (two layers in FIG. 1) are embedded on the outer periphery of the carcass layer 4 in the tread portion 1. Each belt layer 7 includes a plurality of reinforcing cords inclined with respect to the tire circumferential direction, and the reinforcing cords are arranged so as to cross each other between the layers. In these belt layers 7, the inclination angle of the reinforcing cords with respect to the tire circumferential direction is set, for example, in the range of 10° to 40°. Furthermore, at least one belt reinforcing layer 8 (two layers in FIG. 1) is provided on the outer periphery of the belt layer 7. The belt reinforcing layer 8 includes organic fiber cords oriented in the tire circumferential direction. In the belt reinforcing layer 8, the organic fiber cords are set at an angle of, for example, 0° to 5° with respect to the tire circumferential direction.

[0020] As shown in FIG. 2 , the tire of the present invention has an indicia 10 provided on the outer surface of at least one of the pair of sidewall portions 2. The indicia 10 depicts letters, figures, or symbols using the shape of a recess 11 recessed from the outer surface of the sidewall portion 2. The outer surface of the sidewall portion 2 around the indicia 10 (recess 11) is flat, and in the following description, the periphery of the indicia 10 (recess 11) may be referred to as a flat portion 12. Because the present invention is primarily concerned with air release from the periphery (flat portion 12) of the indicia 10 (recess 11), the shape of the indicia 10 (recess 11) itself is not particularly limited. For example, the bottom surface of the indicia 10 (recess 11) may be serrated, formed by an arrangement of multiple parallel ridges (not shown). Furthermore, a serrated portion (not shown), formed by an arrangement of multiple parallel ridges, may be provided around the flat portion 12.

[0021] FIG. 3 shows an example of a tire vulcanizing apparatus including a tire vulcanizing mold (hereinafter, sometimes simply referred to as "mold") of the present invention. The tire vulcanizing apparatus comprises a mold 20 that molds the outer surface of the tire T, and a cylindrical bladder 30 that is inserted inside the pneumatic tire T. This tire vulcanizing apparatus also comprises a heating and pressurizing medium supply means (not shown) that supplies a heating and pressurizing medium such as steam into the bladder 30, and a heating means (not shown) that heats the mold 20. Note that the present invention mainly relates to an exhaust mechanism formed in the side plate 21 described below, and so the structure of the tire vulcanizing apparatus is not limited to the example shown in the figure, as long as it comprises the mold 20 (particularly the side plate 21).

[0022] The mold 20 is composed of a pair of side plates 21 (lower side plate 21A and upper side plate 21B) for molding the sidewall portion 2 of the tire, a pair of bead rings 22 (lower bead ring 22A and upper bead ring 22B) for molding the bead portion 3 of the pneumatic tire T, and a plurality of sectors 23 for molding the tread portion 1 of the pneumatic tire T, and the pneumatic tire T is vulcanized and molded inside the mold 20.

[0023] The heating and pressurizing medium supply means (not shown) is configured to supply steam adjusted to a predetermined temperature and pressure and nitrogen gas adjusted to a predetermined pressure as the heating and pressurizing medium at appropriate times. When such heating and pressurizing medium is introduced into the bladder 30, the pressure of the heating and pressurizing medium presses the pneumatic tire T from the inside toward the inner surface of the mold 20. Note that it is also possible to use only steam as the heating and pressurizing medium.

[0024] The heating means (not shown) is attached to the lower side plate 21, the upper side plate 22, and the sector 23 that make up the mold 20, and the mold 20 is heated by the heating means to vulcanize the pneumatic tire T.

[0025] In the tire vulcanizing apparatus configured as described above, the tire molding mold (mold 20) of the present invention is provided with, on at least one of a pair of side plates 21 (lower side plate 21A and upper side plate 21B) for molding the sidewall portion 2 of the tire T, a convex portion 11' corresponding to the tire indicia 10 (concave portion 11), a flat portion 12' formed adjacent to the convex portion 11', and an air-vent slit 40 formed around the convex portion 11' and opening into the flat portion 12'. The air-vent slit 40 is a minute gap opening into the tire molding surface of the side plate 21, and as shown in FIG. 5, penetrates the mold 20 (side plate 21) and reaches an exhaust mechanism (not shown) within the tire molding mold or the outside of the tire molding mold, thereby discharging air remaining in the mold during tire molding.

[0026] Unlike conventional vent holes (thin cylindrical exhaust holes), these air-release slits 40 hardly allow rubber to flow into them, so spew, as occurs with conventional vent holes, does not occur. Even if traces of the slits 40 are formed due to rubber flowing into the slits 40, they only leave fine linear traces, so they do not mar the appearance or worsen the air resistance around the tire. In particular, the portion of the sidewall portion 2 formed by the flat portion 12' (around the indicia 10) is a region where traces of the exhaust mechanism are easily noticeable because it is flat. However, since almost no slits 40 remain as described above, the tire's appearance can be improved.

[0027] As described above, the slit 40 is a minute gap at the opening, and the width w of the slit 40 is preferably 0.01 mm to 0.5 mm, more preferably 0.02 mm to 0.05 mm. By making the width of the slit 40 sufficiently small, rubber does not substantially flow into the slit 40. Even if traces of the slit 40 remain due to the rubber that has flowed into the slit 40, they only remain as minute linear traces. This prevents damage to the tire's appearance and prevents poor appearance. If the width w of the slit 40 is smaller than 0.01 mm, it becomes difficult to ensure sufficient exhaust performance. Furthermore, the slit 40 is too thin, making it difficult to manufacture a mold (process the slit 40). If the width w of the slit 40 exceeds 0.5 mm, rubber tends to flow into the slit 40, leaving traces of the slit 40.

[0028] In the case of a mold for forming a string of characters consisting of a plurality of display elements 10, as shown in FIG. 4, a series of convex portions (a group of a series of convex portions 11' corresponding to a string of characters) consisting of a plurality of adjacent convex portions 11' sandwiching a flat portion 12' is formed on the side plate 21. Note that while the term "string of characters" is used for convenience, a display element depicts characters, figures, or symbols, and therefore a group of characters, a group of figures, a group of symbols, or a group of display elements combining these all fall under the category of "string of characters." In this embodiment, the maximum value of the tire radial dimension of the convex portions 11' included in the convex portion string is defined as the character height Ch, the maximum value of the tire circumferential dimension of the convex portions 11' included in the convex portion string is defined as the character width Cw, and the larger of the character height Ch and the character width Cw is defined as the maximum dimension A. Furthermore, a peripheral region R is defined as an area surrounded by a pair of imaginary lines extending in the tire radial direction at positions spaced apart by the maximum dimension A outward in the tire circumferential direction from the tire circumferential center positions of the respective protrusions 11' located at both ends in the tire circumferential direction of the protrusion row, and a pair of imaginary lines extending in the tire circumferential direction at positions spaced apart by the maximum dimension A on both sides in the tire radial direction from the tire radial center position of the protrusion 11' having the maximum dimension A. When the peripheral region R is defined in this manner, it is preferable that the slits 40 of the present invention be disposed within the peripheral region R. This allows the slits 40 to be disposed sufficiently close to the protrusions 11', which is advantageous for improving exhaust performance.

[0029] When a single indicator 10 is provided, the tire radial dimension Ch and tire circumferential dimension Cw of one protrusion 11' corresponding to this indicator 10 (depression 11) are compared, and the larger of these is treated as the aforementioned maximum dimension A. In other words, the peripheral region R of one protrusion 11' is a region surrounded by a pair of imaginary lines extending in the tire radial direction at a position spaced apart by the maximum dimension A on both sides of the tire circumferential center of this protrusion 11', and another pair of imaginary lines extending in the tire circumferential direction at a position spaced apart by the maximum dimension A on both sides of the tire radial center. In this case as well, it is preferable to provide a slit 40 within the peripheral region R.

[0030] A plurality of slits 40 may be provided within the peripheral region R. Alternatively, a single slit 40 extending in the tire circumferential direction and / or the tire radial direction may be provided within the peripheral region R. In either case, the total length of the slits 40 in the tire circumferential direction is preferably 30% or more, more preferably 50% or more, of the tire circumferential length of the peripheral region R. Also, the total length of the slits 40 in the tire radial direction is preferably 30% or more, more preferably 50% or more, of the tire radial length of the peripheral region R. By providing the slits with a sufficient length in this way, it is possible to achieve good exhaust performance through the slits.

[0031] As described above, in the case of a mold for forming a string of characters consisting of a plurality of display objects 10, a plurality of convex portions 11' are adjacent to each other with flat portions 12' sandwiched between them. As air tends to accumulate in the flat portions 12' sandwiched between the convex portions 11', it is preferable to provide a slit 40 in this area.

[0032] The slit 40 may be formed directly in the mold 20 (side plate 21). Alternatively, as shown in FIG. 6, the side plate 21 may be configured to include a side plate main body 21a and a replacement piece 21b with the slit 40 formed therein, with the side plate main body 21a provided with a hole into which the replacement piece 21b is inserted. The replacement piece 21b is a component that is removably inserted into a hole formed in the side plate main body 21a. The molding surface of the side plate 21 is formed by inserting and fitting the replacement piece 21b into the hole. Note that FIG. 6 shows the replacement piece 21b inserted into the hole in the side plate main body 21a. In this configuration, the slit 40 can be formed at any position in the replacement piece 21b. However, as shown in the example, it is preferable to form the slit 40 by recessing the surface of the replacement piece 21b that abuts against the side of the hole when fitted, as shown in the example. This configuration makes it easier to clean the inside of the slit 40 when cleaning the mold 20 (especially the side plate 21) after vulcanization, thereby improving productivity.

[0033] The slit 40 can be formed by any method (e.g., wire processing, laser processing, etc.) that can process a minute gap of the above-mentioned dimensions, whether it is formed directly in the side plate 21 or by using the replacement piece 21b as described above.

[0034] When manufacturing a tire using the tire mold described above, a typical method is used, that is, an unvulcanized tire is molded and then vulcanized in the tire mold described above. Air is removed from the mold using the slits 40 described above. Because the slits 40 are tiny gaps through which almost no rubber flows, the tire of the present invention generally leaves no traces of air removal on the surface of the sidewall portion 2 (the area where air is removed using the slits 40). Even if traces of the slits 40 are left behind due to rubber flowing into the slits 40, they are only small, linear traces in a certain area. Even if traces of the slits 40 are formed, they are not easily visible because, as described above, they are small, linear traces, and do not detract from the appearance of the sidewall portion 2. Furthermore, the traces of the slits 40 do not impair the air resistance around the tire.

[0035] As described above, a tire (tire of the present invention) manufactured using the tire mold of the present invention has substantially no traces of the air-bleeding slits 40 remaining, thereby preventing poor appearance and reducing air resistance around the tire. When traces of the slits 40 are present on at least a portion of the surface of the sidewall portion 2, it is preferable that the traces of the slits 40 be present on at least a portion of the surface (flat portion 12) of the sidewall portion 2 surrounding the recessed portion 11 constituting the indicia 10. The surface (flat portion 12) of the sidewall portion 2 surrounding the indicia 10 is a region where traces of the exhaust system are easily noticeable. However, as described above, the traces of the slits 40 are linear traces with a very small width and are not easily visible, and the traces of the slits 40 do not detract from the appearance of the sidewall portion 2. Furthermore, while unevenness on the surface (flat portion 12) of the sidewall portion 2 surrounding the indicia 10 could worsen air resistance around the tire, the traces of the slits 40 are very small, as described above, which is advantageous for reducing air resistance.

[0036] The present invention will be further explained below with reference to examples, but the scope of the present invention is not limited to these examples. [Example]

[0037] In manufacturing tires having a tire size of 245 / 50R19 95Y and the structure illustrated in FIG. 1, the type of exhaust mechanism, the arrangement of the exhaust mechanism, the width of the exhaust mechanism, the ratio of the circumferential length of the exhaust mechanism, the ratio of the radial length of the exhaust mechanism, the presence or absence of inter-character slits, and the method of forming the exhaust mechanism were varied for the tire molding mold, as shown in Tables 1 and 2 (Conventional Example 1, Comparative Example 1, Examples 1 to 12).

[0038] In the "Type of exhaust mechanism" column of Tables 1 and 2, it is noted whether a slit or a vent hole was used as the exhaust mechanism formed in the flat portion adjacent to the convex portion corresponding to the tire's marking (concave portion). Note that if this flat portion did not have an exhaust mechanism, it was marked "none." In the "Location of exhaust mechanism" column, if the slit was located within the peripheral region, it was marked "within peripheral region," and if it was located on the flat portion around the convex portion but outside the peripheral region, it was marked "outside peripheral region." In the "Width of exhaust mechanism" column, the width of the exhaust mechanism used in each mold was recorded. Note that the width of the vent hole is essentially the diameter of the vent hole.

[0039] The "Percentage of Circumferential Length" column in Tables 1 and 2 shows the percentage (unit: %) of the total circumferential length of the slits relative to the circumferential length of the peripheral region. The "Percentage of Radial Length" column shows the percentage (unit: %) of the total radial length of the slits relative to the radial length of the peripheral region. Note that in Example 3, the slits are positioned outside the peripheral region, but the total radial length of the slits is the same as in Examples 1 and 2, and therefore the same values ​​as in Examples 1 and 2 are presented as reference values.

[0040] In the "Presence or absence of inter-character slits" column in Tables 1 and 2, "present" indicates that a slit is provided on the flat portion sandwiched between multiple convex portions included in the convex portion row, and "absent" indicates that no slits are provided between the convex portions. Furthermore, when a slit is provided between all convex portions, it is noted as "all inter-character spaces," and when a slit is provided between some of the convex portions, it is noted as "some." In the "Method of forming the exhaust mechanism" column, "direct" indicates that the exhaust mechanism (slit, vent hole) is provided directly on the side plate, and "replacement piece" indicates that a replacement piece with an exhaust mechanism formed in it is used.

[0041] These examples were evaluated for productivity, appearance, low air resistance, and workability using the following evaluation methods, and the results are shown in Tables 1 and 2.

[0042] Productivity 1,000 tires were vulcanized using each tire molding mold, and the tires were visually inspected immediately after vulcanization to count the number of tires that experienced vulcanization failures due to poor exhaust ventilation, and the incidence of vulcanization failures was calculated. The evaluation results were expressed as an index using the reciprocal of the measured value (incidence of vulcanization failures), with Conventional Example 1's value set at 100. The higher the index value, the fewer tires experienced vulcanization failures, indicating better productivity.

[0043] Appearance For tires that did not experience any vulcanization failures in the above-mentioned productivity evaluation, work such as vent cutting was performed to return them to the state they were in at the time of shipment, and these tires were visually inspected and subjected to a sensory evaluation for appearance defects (such as deterioration in appearance due to cut marks on the spew). The evaluation results were expressed as an index, with Conventional Example 1 being given a value of 100. The higher the index value, the less appearance defects (deterioration in appearance) occurred and the better the appearance.

[0044] Low air resistance The pneumatic tires (test tires) manufactured using each tire molding mold were mounted on wheels with a rim size of 19 x 7.5J, the tire internal pressure was set to 230 kPa, and the tires were mounted on test vehicles. The vehicle speed while coasting was measured in accordance with JIS D1012, and the running resistance was calculated using the multipoint regression method. The evaluation results were expressed as an index using the reciprocal of the measured value, with Conventional Example 1's value being set at 100. The higher the index value, the lower the air resistance, indicating excellent low air resistance.

[0045] Workability The time required to clean the mold (exhaust mechanism) after vulcanizing a tire using each tire mold was measured. The evaluation results were expressed as an index using the reciprocal of the measured value, with Conventional Example 1's value being set at 100. The higher the index value, the shorter the time required to clean the mold, indicating better workability.

[0046] [Table 1]

[0047] [Table 2]

[0048] As is clear from Table 1, when manufactured using the molds of Examples 1 to 12, the appearance and low air resistance were improved and excellent workability was exhibited while productivity (exhaust performance) was maintained or improved, compared to Conventional Example 1. On the other hand, Comparative Example 1 did not have an exhaust mechanism, and therefore vulcanization failures were likely to occur due to poor exhaust, resulting in reduced productivity.

[0049] The present disclosure encompasses the following inventions. Invention [1] A tire molding mold for molding a tire having indicia on the outer surface of a sidewall portion, the indicia depicting letters, figures, or symbols by the shape of a recess recessed from the outer surface of the sidewall portion, the tire molding mold having a side plate for molding the sidewall portion, the side plate having a protrusion corresponding to the recess, a flat portion formed adjacent to the protrusion, and an air vent slit formed around the protrusion so as to open into the flat portion. Invention [2] The tire mold according to invention [1], wherein the width of the slit is 0.01 mm to 0.5 mm. Invention [3] A plurality of the protrusions form a series of protrusion rows, a maximum value of the radial dimension of the convex portion included in the convex portion row is defined as a character height Ch; The maximum value of the tire circumferential dimension of the convex portion included in the convex portion row is defined as a character width Cw, The larger of the character height Ch and the character width Cw is defined as the maximum dimension A, When a peripheral region is defined as a region surrounded by a pair of imaginary lines extending in the tire radial direction at positions spaced apart by the maximum dimension A outward in the tire circumferential direction from the tire circumferential center positions of the respective convex portions located at both ends in the tire circumferential direction of the convex portion row, and a pair of imaginary lines extending in the tire circumferential direction at positions spaced apart by the maximum dimension A on both sides in the tire radial direction from the tire radial center position of the convex portion having the maximum dimension A, The tire mold according to invention [1] or [2], wherein the slit is disposed within the peripheral region. Invention [4] A tire molding mold according to invention [3], characterized in that the total length of the slits in the tire circumferential direction is 30% or more of the length of the peripheral region in the tire circumferential direction. Invention [5] A tire molding mold according to invention [3] or [4], characterized in that the total length of the slits in the tire radial direction is 30% or more of the length of the peripheral region in the tire radial direction. Invention [6] A tire molding mold according to any one of inventions [3] to [5], characterized in that the slit is provided in the flat portion sandwiched between the plurality of convex portions included in the convex portion row. Invention [7] A tire molding mold according to any one of inventions [1] to [6], characterized in that it comprises a spare piece in which at least one of the slits is formed, and a hole formed in the side plate into which the spare piece is inserted. Invention [8] A method for manufacturing a tire using a tire mold according to any one of Inventions [1] to [7], characterized in that an unvulcanized tire is placed in the tire mold, and the unvulcanized tire is vulcanized in the tire mold while air is removed through the slits. Invention [9] A tire manufactured by the tire manufacturing method according to Invention [8], A tire having a trace of the slit on at least a part of the surface of the sidewall portion around the recess that constitutes the indicia. [Explanation of symbols]

[0050] 1 Tread section 2 Sidewall 3 Bead section 4 carcass layers 5 bead core 6 Bead filler 7 Belt Layer 8 Belt reinforcement layer 10 Display items 11 Recess 12 Flat area 11' convex part 12' flat part 20 Mold 21 Side Plate 22 bead ring 23 sectors 30 Bladder 40 slits CL Tire Equator

Claims

1. A tire molding mold for molding a tire having indicia on the outer surface of a sidewall portion, the indicia depicting letters, figures, or symbols by the shape of a recess recessed from the outer surface of the sidewall portion, the tire molding mold having a side plate for molding the sidewall portion, the side plate having a protrusion corresponding to the recess, a flat portion formed adjacent to the protrusion, and an air vent slit formed around the protrusion so as to open into the flat portion.

2. 2. The tire mold according to claim 1, wherein the width of the slit is 0.01 mm to 0.5 mm.

3. a plurality of the protrusions form a series of protrusion rows, a maximum value of the radial dimension of the convex portion included in the convex portion row is defined as a character height Ch; a character width Cw is a maximum value of the circumferential dimension of the convex portion included in the convex portion row, The larger of the character height Ch and the character width Cw is defined as the maximum dimension A, When a peripheral region is defined as a region surrounded by a pair of imaginary lines extending in the tire radial direction at positions spaced apart by the maximum dimension A outward in the tire direction from the tire circumferential center positions of the respective convex portions located at both ends in the tire circumferential direction of the convex portion row, and a pair of imaginary lines extending in the tire circumferential direction at positions spaced apart by the maximum dimension A on both sides in the tire radial direction from the tire radial center position of the convex portion having the maximum dimension A, 2. The tire mold of claim 1, wherein the slit is located within the peripheral region.

4. 4. The tire mold according to claim 3, wherein the total length of the slits in the tire circumferential direction is 30% or more of the length of the peripheral region in the tire circumferential direction.

5. 4. The tire mold according to claim 3, wherein the total length of the slits in the tire radial direction is 30% or more of the length of the peripheral region in the tire radial direction.

6. 4. The tire mold according to claim 3, wherein the slit is provided in the flat portion sandwiched between the plurality of convex portions included in the convex portion row.

7. 2. The tire molding mold according to claim 1, further comprising: a spare piece having at least one of the slits formed therein; and a hole formed in the side plate into which the spare piece is inserted.

8. A tire manufacturing method using the tire molding mold according to any one of claims 1 to 7, characterized in that an unvulcanized tire is placed in the tire molding mold, and the unvulcanized tire is vulcanized in the tire molding mold while air is removed through the slits.

9. A tire manufactured by the tire manufacturing method according to claim 8, A tire having a trace of the slit on at least a part of the surface of the sidewall portion around the recess that constitutes the indicia.

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