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 exhibiting 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 serration region 10 formed by arranging a plurality of ridges 11 on the outer surface of a sidewall part 2 and a plane region 12 composed of a smooth surface provided adjacently to the serration region 10, wherein an air vent slit 40 opening to the tire forming surface of a side plate 21 and extending along a boundary extending in the tire circumferential direction between the serration region 10 and the plane region 12 on the side plate 21 for forming the sidewall part 2 is provided in at least a part along the boundary.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] In pneumatic tires, serrations are formed on the sidewall by arranging numerous ridges in order to make unevenness in the sidewall less noticeable and to improve the decorativeness and visibility of the sidewall (see, for example, Patent Document 1). Considering the effect on air resistance around the tire, it is preferable that such serrations have a small ridge height, but there is a concern that a small ridge height may increase the likelihood of malfunctions (light malfunctions) caused by air pockets during vulcanization in the areas where the serrations are provided.

[0003] To address this issue, vent holes (thin exhaust holes) are provided adjacent to the serrated areas. However, when exhausting air using vent holes, rubber may flow into the vent holes, potentially resulting in spews, or whisker-like protrusions, on the surface of the molded tire. Although such spews are removed before the tire is shipped, even after the spews are removed, traces of the spew removal (cut marks), such as minute cylindrical protrusions at the base of the spew, may remain on the tire surface. The presence of such cut marks can adversely affect the tire's appearance, and there is concern that minute irregularities on the tire surface caused by the cut marks may affect the air resistance around the tire. Therefore, there is a need for further measures to efficiently exhaust air during vulcanization in serrated tires without affecting the tire's appearance or air resistance around the tire. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 3645358 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a tire molding mold that makes it possible to improve the tire appearance and the air resistance around the tire while exhibiting good exhaust performance, a tire manufacturing method using the same, and a tire. [Means for solving the problem]

[0006] In order to achieve the above object, the tire molding mold of the present invention is a tire molding mold for molding a tire having a serration region formed by an arrangement of a plurality of ridges on the outer surface of a sidewall portion, and a plain region consisting of a smooth surface provided adjacent to the serration region, and is characterized in that at least a part of the boundary extending in the tire circumferential direction between the serration region and the plain region in a side plate for molding the sidewall portion is provided with an air vent slit that opens on the tire molding surface of the side plate and extends along the boundary.

[0007] The tire manufacturing method of the present invention for achieving the above-mentioned 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 the slits.

[0008] 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 the slits in at least a portion of the boundary extending in the tire circumferential direction between the serration region and the plain region. [Effects of the Invention]

[0009] 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 the conventional vent holes, it is possible to maintain good venting performance, prevent poor appearance, and reduce air resistance around the tire. Specifically, with conventional vent holes, rubber may flow into the vent holes, causing spew, and even if 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 slits are tiny gaps, rubber is less likely to flow into them. Even if a mark remains due to rubber that has flowed into the slit, it is only a very narrow 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 at the boundary between the serration region and the plain region as described above, it is possible to efficiently vent air from the serration region, prevent poor appearance, and reduce air resistance around the tire.

[0010] The tire manufacturing method of the present invention uses the tire molding mold of the present invention described above, and therefore air remaining in the mold (particularly in the serration region) 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 the tire appearance is not impaired and air resistance around the tire can be reduced.

[0011] 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.

[0012] 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.

[0013] In the tire mold of the present invention, the ratio of the total length of the slits in the tire circumferential direction to the length of the boundary between the serration region and the plain region in the tire circumferential direction is preferably 30% or more. By providing the slits with a sufficient length in this manner, it is possible to achieve good exhaust performance through the slits.

[0014] The tire mold of the present invention can also be designed with auxiliary slits for venting air that open to the tire molding surface of the side plate and extend along the recesses for forming the ridges. This can further improve exhaust performance. Furthermore, even if traces of the slits remain due to rubber that has flowed into the auxiliary slits, these traces are merely fine linear traces extending along the ridges, and therefore do not impair the decorativeness or visibility of the serration area.

[0015] In the above specifications, it is preferable that a plurality of auxiliary slits are arranged at intervals in the tire circumferential direction, and that the pitch of the auxiliary slits in the tire circumferential direction is 5 mm to 300 mm. This allows for a sufficient number of auxiliary slits, which is advantageous for improving exhaust performance.

[0016] 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]

[0017] [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 a side view showing an example of a tire according to an embodiment of the present invention. [Figure 3] FIG. 2 is a cross-sectional view showing an example of a serration region formed in a sidewall portion of a tire according to an embodiment of the present invention. [Figure 4] 1 is an explanatory diagram showing an example of a tire vulcanizing apparatus including a tire molding mold of the present invention. FIG. [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

[0018] The configuration of the present invention will be described in detail below with reference to the accompanying drawings.

[0019] 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.

[0020] 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.

[0021] As shown in FIG. 2, a serrated region 10 is formed on the outer surface of the sidewall portion 2 of the present invention. The serrated region 10 is a serrated region formed by an arrangement of multiple parallel ridges 11. The shape of the ridges 11 is not particularly limited, but for example, as shown in FIG. 3, the ridges 11 have a triangular cross section. The width w of each ridge 11 (the width in a direction perpendicular to the extension direction of the ridge 11) can be set to, for example, 0.3 mm to 5 mm. The height h from the valley between adjacent ridges 11 to the apex of the ridge 11 can be set to, for example, 0.10 mm to 1.0 mm. In the serrated region 10, the valley between adjacent ridges 11 is recessed below the reference plane of the sidewall portion 2 (the plain region 12 described below). Note that the serrated region 10 is a band-shaped, annular region as shown in FIG. 2, and the outer surface of the sidewall portion 2 is rounded as shown in FIG. 1. Therefore, the multiple ridges 11 do not need to be perfectly parallel, and an inclination of about ±5° is permitted.

[0022] As shown in Figure 2, the outer surface of the sidewall portion 2 of the present invention has a plain region 12 formed adjacent to the serration region 10. The plain region 12 is a surface of the sidewall portion 2 that is not serrated. The sidewall portion 2 may be provided with projections or recesses other than the serrations, and the plain region 12 is the reference surface of the sidewall portion 2 that serves as the basis for the protrusions or depressions of these projections or recesses.

[0023] FIG. 4 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).

[0024] 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 of the tire, a pair of bead rings 22 (lower bead ring 22A and upper bead ring 22B) for molding the bead portion of the pneumatic tire T, and a plurality of sectors 23 for molding the tread portion of the pneumatic tire T, and the pneumatic tire T is vulcanized and molded inside the mold 20.

[0025] 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.

[0026] 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.

[0027] In the tire vulcanizing apparatus configured as described above, the tire molding mold (mold 20) of the present invention has recesses 11' corresponding to the serration regions 10 (ridges 11) of the tire, as shown in FIG. 5 , 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. Each recess 11' has a shape that is an inverted version of the ridge 11, and multiple recesses 11' are arranged parallel to one another, similar to the ridges 11. The tire molding surface adjacent to the region where multiple recesses 11' are arranged (corresponding to the serration regions 10) corresponds to the plain region 12. An air-bleeding slit 40 is formed at the boundary between these regions (regions corresponding to the serration regions 10 and the plain region 12). In the serration region 10 (see Figure 3) of a tire manufactured using the illustrated mold, the valleys formed between adjacent ridges 11 are recessed below the reference surface (region 12) of the sidewall portion 2, so in the mold 20 (side plate 21) of Figure 5, the deepest parts (corresponding to the apexes of the ridges 11) of the recesses 11' are approximately flush with the molding surface of the side plate 21 (for this reason, although it appears that there are an array of multiple protrusions protruding from the molding surface of the side plate 21, these are actually a series of arranged recesses 11').

[0028] The air-bleeding slits 40 are minute gaps that open into the tire molding surface of the side plate 21. As shown in FIG. 5 , they penetrate the mold 20 (side plate 21) and reach an exhaust mechanism (not shown) inside the tire molding mold or the outside of the tire molding mold, thereby discharging air remaining in the mold during tire molding. The slits 40 extend along at least the boundary between the serration region 10 and the plain region 12 that extends in the tire circumferential direction. A single slit 40 may be provided that extends the entire length of the boundary between the serration region 10 and the plain region 12 that extends in the tire circumferential direction, or multiple slits 40 may be provided intermittently along this boundary. As shown in FIG. 2 , the serration region 10 also has boundaries that extend in the tire radial direction (both ends of the serration region 10 in the tire circumferential direction), and slits 40 may also be provided at these boundaries that extend in the tire radial direction, similar to the boundaries that extend in the circumferential direction.

[0029] Unlike conventional vent holes (thin cylindrical exhaust holes), these air-release slits 40 allow almost no rubber to flow into them, preventing the spewing that occurs with conventional vent holes. Even if traces of the slits 40 are left behind due to rubber that has flowed into the slits 40, these traces are merely fine, linear traces, so they do not mar the tire's appearance or worsen air resistance around the tire. In particular, in the present invention, the slits 40 are formed at the boundary between the serration region 10 and the plain region 12, extending in the tire circumferential direction, allowing for efficient exhaust from the serration region 10, where air is likely to accumulate, and effectively preventing vulcanization failures in the serration region 10.

[0030] As described above, the slit 40 is a minute gap at the opening, and the width Ws 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.

[0031] The slits 40 should preferably have a sufficient length. In particular, the ratio of the total circumferential length of the slits to the circumferential length of the boundary between the serration region 10 and the plain region 12 should preferably be 30% or more, more preferably 50% or more. In the example of FIG. 2 , there are a pair of circumferential boundaries between the serration region 10 and the plain region 12 on the inner and outer sides in the tire radial direction. For example, the ratio of the total circumferential length of the slit 40 provided at the boundary on the inner side in the tire radial direction is calculated based on the length L1 of the boundary on the inner side in the tire radial direction. Similarly, the ratio of the total circumferential length of the slit 40 provided at the boundary on the outer side in the tire radial direction is calculated based on the length L2 of the boundary on the inner side in the tire radial direction. By providing the slits 40 with a sufficient length in this way, the slits 40 can exhibit excellent exhaust performance. If the total circumferential length of the slits 40 is less than 30% of the circumferential length of the boundary, the slits 40 may not be long enough, which may result in reduced exhaust performance.

[0032] When additional slits 40 are provided at boundaries extending in the tire radial direction (both ends of the serration region 10 in the tire circumferential direction), these slits 40 should also have a sufficient length. Specifically, as in the case described above, the ratio of the total tire radial length of the slits 40 to the tire circumferential length of the boundaries extending in the tire radial direction of the serration region 10 and the plain region 12 should preferably be 30% or more, more preferably 50% or more. In this case, too, the ratio should be calculated for each boundary. In this case, too, the slits 40 can be sufficiently long, making it possible to exhibit good exhaust performance through the slits 40.

[0033] In addition to the slits 40 described above, an auxiliary slit (not shown) for venting air can also be provided in the tire molding surface of the side plate 21, extending along the recess 11' corresponding to the ridge 11. The auxiliary slit is preferably connected to the slit 40 provided at the boundary extending in the tire circumferential direction. Providing an auxiliary slit adds an air exhaust path, further improving exhaust performance. The auxiliary slit can have the same dimensions as the slit 40 described above. The auxiliary slit also has a sufficiently small width that rubber does not substantially flow into it, leaving no traces. Even if traces of the auxiliary slit remain due to rubber flowing into it, in this specification, they are merely fine linear traces extending along the ridge 11, and therefore appear to blend in with the ridge 11, without impairing the decorativeness or visibility of the serration region 10.

[0034] When providing auxiliary slits as described above, it is preferable to arrange a plurality of auxiliary slits at intervals in the tire circumferential direction, and in particular, it is preferable that the auxiliary slits be spaced apart in the tire circumferential direction at a pitch of preferably 5 mm to 300 mm, more preferably 20 mm to 150 mm. By providing the auxiliary slits at such intervals, a sufficient number of auxiliary slits are provided inside the serration region 10, which is advantageous for improving exhaust performance.

[0035] 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.

[0036] 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.

[0037] 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 (particularly the area corresponding to the serration region 10) through the slits 40 described above. Because the slits 40 are tiny gaps, almost no rubber flows into them. Therefore, in the tire of the present invention, no traces resulting from air removal are generally formed on the surface of the sidewall portion 2 (areas where air is removed using the slits 40). Even if traces of the slits 40 are formed due to rubber flowing into the slits 40, they are merely linear traces with a fine width. Even if traces of the slits 40 are formed, because they are linear traces with a fine width, they are not easily visible, and the appearance of the sidewall portion 2 is not impaired by the traces of the slits 40. Furthermore, the traces of the slits 40 do not impair the air resistance around the tire.

[0038] As described above, a tire manufactured using the tire mold of the present invention (tire of the present invention) has substantially no traces of the air-bleeding slits remaining, thereby preventing poor appearance and reducing air resistance around the tire. When traces of the slits are present on at least a portion of the surface of the sidewall portion, it is preferable that traces of the slits 40 are present on at least a portion of the boundary extending in the tire circumferential direction between the serration region 10 and the plain region 12. Even if traces of the slits 40 remain in this way, they are merely fine linear traces left on the boundary between the two regions, and therefore do not result in poor appearance or increased air resistance.

[0039] 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]

[0040] In manufacturing tires having a tire size of 245 / 50R19 95Y and having the structure illustrated in FIG. 1 and including a serration region (and a plain region) in the sidewall portion, the tire molding molds were varied in terms of the type of exhaust mechanism, the width of the exhaust mechanism, the length of the exhaust mechanism, the arrangement of the exhaust mechanism, the presence or absence of auxiliary slits, and the method of forming the exhaust mechanism, as shown in Tables 1 to 2 (Conventional Example 1, Comparative Examples 1 to 4, Examples 1 to 8).

[0041] The "Type of exhaust mechanism" column in Tables 1 and 2 indicates whether a slit, vent hole, or circumferential groove was used as the exhaust mechanism. Note that a circumferential groove is a groove provided in a position described in the "Location of exhaust mechanism" column described below, and is basically an exhaust mechanism used in combination with a vent hole (connecting vent holes to facilitate air flow) as in Conventional Example 1 (Comparative Example 2 only has a circumferential groove, so does not actually function as an exhaust mechanism, but is presented for comparison).

[0042] The "Exhaust Mechanism Width" column in Tables 1 and 2 lists the width of the exhaust mechanism employed in each mold. The vent hole width essentially refers to the diameter of the vent hole. The "Exhaust Mechanism Length" column lists the length of the exhaust mechanism employed in each mold. The vent hole length essentially refers to the diameter of the vent hole and is listed as a real value (unit: mm). The lengths of the slits and circumferential grooves are the sum of their respective lengths in the tire circumferential direction, and are shown as a percentage (unit: %) of the tire circumferential length of the boundary between the serration region and the plain region extending in the tire circumferential direction. Comparative Examples 3 and 4 are examples in which the exhaust mechanism (slit) is not provided on the boundary, but because slits of the same length as in Example 3 were provided, the same values ​​as in Example 3 are listed for convenience. In the "Exhaust Mechanism Width" and "Exhaust Mechanism Length" columns, when a circumferential groove and a vent hole were provided in combination, the numerical values ​​for the circumferential groove are listed in the upper row of each column, and the numerical values ​​for the vent hole are listed in the lower row.

[0043] In the "Location of exhaust mechanism" column of Tables 1 and 2, when the exhaust mechanism is provided on the boundary (both inside and outside in the tire radial direction) between the serration region and the plain region extending in the tire circumferential direction, it is indicated as "on the boundary," when it is provided at a position 5 mm away from this boundary (both inside and outside in the tire radial direction) toward the plain region, it is indicated as "away from the boundary," and when it is provided within the serration region, it is indicated as "inside the serration region." Note that auxiliary slits are always provided within the serration region, but the slits indicated for location in this column are slits extending in the tire circumferential direction other than the auxiliary slits.

[0044] In the "Auxiliary slit presence / absence" column in Tables 1 and 2, cases where an auxiliary slit for air venting extending along the ridge is provided are marked "Yes," and cases where this auxiliary slit is not provided are marked "No." When an auxiliary slit is provided, the width of the auxiliary slit is the same as the width of the slit in that example, and in all cases the auxiliary slit pitch was set to 80 mm. In the "Exhaust mechanism formation method" column, cases where the exhaust mechanism (slit, vent hole, circumferential groove) is provided directly on the side plate are marked "Direct" and cases where a replacement piece with an exhaust mechanism formed in it is used are marked "Replacement piece."

[0045] These examples were evaluated for appearance defect prevention, low air resistance, and workability using the following evaluation methods, and the results are shown in Table 1.

[0046] Prevents appearance defects 1,000 tires were vulcanized using each tire mold, and the resulting tires were visually inspected to count the number of tires with visual defects (poor rubber flow or poor aesthetics due to incorrect vent cutting) and determine the incidence of visual defects. The evaluation results were expressed as an index using the reciprocal of the measured value, with Conventional Example 1's value being 100. The higher the index value, the fewer tires with visual defects, meaning better prevention of visual defects.

[0047] 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.

[0048] 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.

[0049] [Table 1]

[0050] [Table 2]

[0051] As is clear from Tables 1 and 2, when manufactured using the molds of Examples 1 to 8, poor appearance was suppressed to the same extent or more than in Conventional Example 1, while air resistance was reduced and excellent workability was demonstrated. On the other hand, Comparative Example 1 had only vent holes, which reduced the ability to prevent poor appearance. Comparative Example 2 had only circumferential grooves, which reduced the ability to prevent poor appearance. Comparative Example 3 employed slits as an exhaust mechanism, but because these slits were not provided at the boundary between the serration region and the plain region extending in the tire circumferential direction, the slits did not contribute to exhaust within the serration region and were unable to prevent poor appearance. Comparative Example 4 employed slits as an exhaust mechanism, but because these slits were provided within the serration region and extended so as to intersect with the ridges, they were unable to prevent poor appearance.

[0052] The present disclosure includes the following inventions. Invention [1] A tire mold for molding a tire having a serration region formed by arranging a plurality of ridges on the outer surface of a sidewall portion, and a plain region formed by a smooth surface adjacent to the serration region, a tire molding mold comprising: a side plate for molding the sidewall portion, the side plate having an air-bleeding slit in at least a portion of a boundary extending in the tire circumferential direction between the serration region and the plain region, the air-bleeding slit opening on the tire molding surface of the side plate and extending along the boundary. 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 tire molding mold according to invention [1] or [2], characterized in that the ratio of the total length of the slits in the tire circumferential direction to the length of the boundary in the tire circumferential direction is 30% or more. Invention [4] A tire molding mold according to any one of Inventions [1] to [3], characterized in that an auxiliary slit for air release is provided, the auxiliary slit opening on the tire molding surface of the side plate and extending along the recess for forming the ridge. Invention [5] A tire molding mold according to invention [4], characterized in that a plurality of the auxiliary slits are arranged at intervals in the tire circumferential direction, and the pitch of the auxiliary slits in the tire circumferential direction is 5 mm to 300 mm. Invention [6] A tire molding mold according to any one of inventions [1] to [5], 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 [7] A method for manufacturing a tire using a tire mold according to any one of Inventions [1] to [6], 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 [8] A tire manufactured by the tire manufacturing method according to Invention [7], A tire having a trace of the slit in at least a part of a boundary between the serration region and the plain region extending in the tire circumferential direction. [Explanation of symbols]

[0053] 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 Serration Area 11 Ridge 12 Plain Area 20 Mold 21 Side Plate 22 bead ring 23 sectors 30 Bladder 40 slits CL Tire Equator

Claims

1. A tire mold for molding a tire having a serration region formed by arranging a plurality of ridges on an outer surface of a sidewall portion, and a plain region formed by a smooth surface adjacent to the serration region, a tire molding mold comprising: a side plate for molding the sidewall portion, the side plate having an air-bleeding slit in at least a portion of a boundary extending in the tire circumferential direction between the serration region and the plain region, the air-bleeding slit opening on the tire molding surface of the side plate and extending along the boundary.

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

3. 2. The tire mold according to claim 1, wherein a ratio of a total length of the slits in the tire circumferential direction to a length of the boundary in the tire circumferential direction is 30% or more.

4. 2. The tire mold according to claim 1, wherein an auxiliary slit for air release is provided in the tire molding surface of the side plate and extends along the recess for forming the ridge.

5. 5. The tire mold according to claim 4, wherein a plurality of the auxiliary slits are arranged at intervals in the tire circumferential direction, and the pitch of the auxiliary slits in the tire circumferential direction is 5 mm to 300 mm.

6. 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.

7. A tire manufacturing method using the tire molding mold according to any one of claims 1 to 6, 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.

8. A tire manufactured by the tire manufacturing method according to claim 7, A tire having a trace of the slit in at least a part of a boundary between the serration region and the plain region extending in the tire circumferential direction.

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