Tire mold, tire manufacturing method using the same, and tire

Abstract

To provide a mold for molding a tire capable of suppressing an appearance defect caused by an exhaust mark at the time of vulcanization while suppressing a vulcanization defect and capable of reducing the air resistance of the tire, a method for manufacturing the tire using the same, and the tire.SOLUTION: The tire mold 20 of the present invention includes the side plate 21 for forming the sidewall portion 2 of the tire T, the forming surface S of the side plate 21 has the outer area Ao and the inner area Ai with the tire maximum-width position Pmax as the boundary, the side plate 21 has at least one slit 26 for air bleeding in at least the outer area Ao, and the number S1 of the slits 26 disposed in the outer area Ao is larger than the number S2 of the slits 26 disposed in the inner area Ai.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a tire molding mold for molding tires, a tire manufacturing method using the same, and a tire; and more particularly, to a tire molding mold that makes it possible to suppress poor vulcanization while suppressing poor tire appearance and reducing tire air resistance, a tire manufacturing method using the same, and a tire. [Background technology]

[0002] When manufacturing a tire, an unvulcanized tire is placed in a mold and vulcanized within the mold. If air remains between the molding surface of the mold and the unvulcanized tire, the tire and the mold do not make sufficient contact in the air pockets, resulting in poor vulcanization. Poor vulcanization refers to an abnormal appearance caused by an unexpected flow of rubber during tire vulcanization. While this does not affect tire performance, correcting the abnormal appearance requires a long period of additional work, which is undesirable from the perspective of production efficiency. Therefore, numerous cylindrical vent holes are formed on the molding surface of the mold, and air remaining between the molding surface of the mold and the unvulcanized tire is exhausted through these vent holes (see, for example, Patent Document 1).

[0003] However, when vent holes are provided in the mold, the spew formed by the rubber that has flowed into the vent holes must be removed after vulcanization. Furthermore, even after removal, the spew cut marks remain visible, marring the tire's appearance. Furthermore, the spew cut marks increase the tire's air resistance. Therefore, there is a need to minimize the number of vent holes while still ensuring sufficient exhaust performance. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2020-168788 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 can suppress poor vulcanization while suppressing poor appearance caused by exhaust marks during vulcanization and reducing the air resistance of the tire, as well as a tire manufacturing method and tire using the same. [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, comprising side plates for molding the sidewall portion of the tire, the molding surface of the side plates having outer and inner regions bounded by the maximum width position of the tire, the side plates having at least one air-bleeding slit in at least the outer region, and the number S1 of slits arranged in the outer region being greater than the number S2 of slits arranged in the inner region.

[0007] Furthermore, in order to achieve the above object, the tire manufacturing method of the present invention is a tire manufacturing method using the tire molding mold described above, 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] Furthermore, in order to achieve the above object, the tire of the present invention is a tire manufactured by the above-mentioned tire manufacturing method, characterized in that the surface of the sidewall portion has traces of the slits. [Effects of the Invention]

[0009] As a result of extensive research into exhaust methods for tire molds, the inventors discovered that by providing a slit-shaped exhaust mechanism instead of the conventional vent holes, it is possible to suppress poor vulcanization, reduce the appearance defects caused by exhaust marks during vulcanization, and reduce the tire's air resistance. Specifically, with conventional vent holes, rubber can 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 slit is a tiny gap, rubber is less likely to flow into it. Furthermore, 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's appearance is not impaired and the tire's air resistance is not adversely affected. Furthermore, the conventional process of removing the spew after vulcanization is unnecessary.

[0010] The present invention is based on this finding, and proposes that the molding surface of a side plate have an outer region and an inner region bounded by the tire's maximum width position, and that the side plate have at least one air-vent slit in at least the outer region, allowing air remaining between the tire and the side plate to be exhausted through the slit. This prevents poor curing, suppresses poor appearance due to exhaust marks during curing, and reduces the tire's air resistance. In particular, the number S1 of slits in the outer region, which has a relatively greater effect on air resistance, is greater than the number S2 of slits in the inner region, thereby enhancing the effect of reducing air resistance. Note that the present invention allows for the formation of cylindrical vent holes in the side plate, but aims to achieve the above-mentioned effects by replacing at least some of the vent holes with slits.

[0011] In the tire mold of the present invention, the side plates preferably have at least one air-bleeding slit in each of the outer and inner regions. By providing slits not only in the outer region but also in the inner region, poor tire appearance can be effectively suppressed and the air resistance of the tire can be effectively reduced.

[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 small, 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. The slit width is the dimension measured along the short side of the slit.

[0013] In the tire mold of the present invention, the slit length is preferably 0.6 mm to 13.0 mm. By making the slit length sufficiently large, 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. The slit length is the dimension measured along the longitudinal direction of the slit.

[0014] In the tire mold of the present invention, it is preferable that the side plates have a circumferential groove extending in the circumferential direction and having a depth of 0.3 mm to 5.0 mm and a width of 0.1 mm to 5.0 mm, and that at least one of the slits communicate with the circumferential groove. When such a circumferential groove is provided, it is possible to reduce the number of slits and vent holes formed in the side plates, thereby reducing the number of steps in manufacturing the mold.

[0015] In the tire mold of the present invention, the side plates preferably have radial grooves extending radially across the maximum width position of the tire and having a depth of 0.3 mm to 5.0 mm and a width of 0.1 mm to 5.0 mm, with the ends of the radial grooves in their outer regions communicating with one of the slits and the ends of the radial grooves in their inner regions communicating with a cylindrical vent hole. When such radial grooves are provided, it is possible to reduce the number of slits and vent holes formed in the side plates, thereby reducing the number of steps in mold production.

[0016] In the tire molding die of the present invention, it is preferable that the number S1 of slits arranged in the outer region and the number V1 of cylindrical vent holes arranged in the outer region satisfy the relationship of 0.5 < S1 / (S1 + V1) ≤ 1.0, and the number S2 of slits arranged in the inner region and the number V2 of cylindrical vent holes arranged in the inner region satisfy the relationship of 0 < S2 / (S2 + V2) ≤ 0.5. Considering the improvement of appearance defects and the reduction of air resistance, it is desirable to increase the ratio of the number S1 of slits arranged in the outer region and the number S2 of slits arranged in the inner region. However, if the ratio becomes excessively high, the manufacturing process of the slits increases and the manufacturing efficiency of the die decreases. On the other hand, by satisfying the above ratio, it is possible to minimize the decrease in die manufacturing efficiency while realizing the improvement of appearance defects and the reduction of air resistance.

[0017] In the tire molding die of the present invention, it is preferable that the side plate has a replacement piece in which at least one slit is formed and a hole portion into which the replacement piece is inserted. By providing a replacement piece in which a slit is formed, the replacement piece can be removed and the cleaning operation can be performed when cleaning the die after vulcanization, so that the workability during cleaning can be improved.

[0018] According to the method for manufacturing a tire of the present invention, using the above-described tire molding die, an unvulcanized tire is put into the tire molding die, and while performing air venting through the slit, the unvulcanized tire is vulcanized in the tire molding die, thereby suppressing vulcanization defects, suppressing appearance defects caused by exhaust marks during vulcanization, and reducing the air resistance of the tire.

[0019] The tire of the present invention is a tire manufactured by the above-described method for manufacturing a tire, and has traces of slits on the surface of the sidewall portion. Such a tire has few vulcanization defects, has a good appearance as a tire product at the shipping stage, and has a small air resistance.

Brief Description of the Drawings

[0020] [Figure 1]1 is a meridian cross-sectional view showing a pneumatic tire according to an embodiment of the present invention. [Figure 2] FIG. 2 is a side view showing a part of the pneumatic tire of FIG. 1 in the circumferential direction. [Figure 3] 1 is a cross-sectional view showing an example of a tire vulcanizing apparatus including a tire molding mold of the present invention. [Figure 4] FIG. 4 is an enlarged plan view showing a main part of the tire mold of FIG. 3. [Figure 5] FIG. 10 is a cutaway perspective view showing an example of a side plate having a slit. [Figure 6] FIG. 10 is a cutaway perspective view showing a modified example of a side plate having a slit. [Figure 7] FIG. 10 is a plan view showing a modified example of a tire mold. DETAILED DESCRIPTION OF THE INVENTION

[0021] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to the accompanying drawings, in which: Figures 1 and 2 show a pneumatic tire according to an embodiment of the present invention.

[0022] As shown in FIG. 1, the pneumatic tire T of this embodiment includes a tread portion 1 extending circumferentially in a ring shape, a pair of sidewall portions 2, 2 arranged on both sides of the tread portion 1, and a pair of bead portions 3, 3 arranged radially inward of the sidewall portions 2.

[0023] A carcass layer 4 is mounted between the pair of bead portions 3, 3. This carcass layer 4 includes a plurality of reinforcing cords extending in the tire radial direction, and is folded back from the inside to the outside of the tire around a bead core 5 disposed in each bead portion 3. Organic fiber cords such as polyester cords are preferably used as the reinforcing cords of the carcass layer 4. A bead filler 6 made of a rubber composition and having a triangular cross section is disposed on the outer periphery of the bead core 5.

[0024] On the other hand, multiple belt layers 7 are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. These belt layers 7 include multiple reinforcing cords that are inclined with respect to the tire circumferential direction, and are arranged so that the reinforcing cords cross each other between the layers. In the belt layers 7, the inclination angle of the reinforcing cords with respect to the tire circumferential direction is set to a range of 10° to 40°, for example. Steel cords are preferably used as the reinforcing cords of the belt layers 7. At least one belt cover layer 8 is arranged on the outer peripheral side of the belt layer 7, with the aim of improving high-speed durability, and the reinforcing cords are arranged at an angle of, for example, 5° or less with respect to the tire circumferential direction. As the reinforcing cords of the belt cover layer 8, organic fiber cords such as nylon and aramid are preferably used.

[0025] The above-described tire internal structure is a typical example of a pneumatic tire, but is not limited to this.

[0026] A plurality of main grooves 11 extending in the tire circumferential direction are formed in the tread portion 1. A plurality of rows of land portions 12 are defined in the tread portion 1 by these main grooves 11. Furthermore, a plurality of lug grooves 13 extending in the tire width direction are formed in at least the land portions 12 located on the outermost sides in the width direction of the tread portion 1. A plurality of shoulder blocks 14 are defined in the land portions 12 located on the outermost sides in the width direction of the tread portion 1 by these lug grooves 13 (see FIG. 2).

[0027] 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, and FIG. 4 shows an enlarged view of the main parts thereof. This 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 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 a side plate 21, which will be described later, and therefore the structure of the tire vulcanizing apparatus is not limited to the example shown, as long as it comprises a mold 20 (particularly a side plate 21).

[0028] The mold 20 is composed of a pair of side plates 21 for molding the sidewall portion 2 of the tire T, a pair of bead rings 22 for molding the bead portion 3 of the tire T, and a plurality of sectors 23 for molding the tread portion 1 of the tire T, and the tire T is vulcanized and molded inside the mold 20.

[0029] 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 tire T is pressed from the inside toward the inner surface of the mold 20 based on the pressure. Note that it is also possible to use only steam as the heating and pressurizing medium.

[0030] Heating means (not shown) is attached to the side plates 21 and sectors 23 that constitute the mold 20, and the tire T is vulcanized by heating the mold 20 with the heating means.

[0031] In the tire vulcanization apparatus configured as described above, at least one of the pair of side plates 21 constituting the mold 20 has a plurality of vent holes 25 and a plurality of slits 26 formed to open onto its molding surface S, as shown in FIGS. 3 and 4 . These vent holes 25 and slits 26 communicate with the outside of the mold 20, for example, via an air passage 27. The vent holes 25 are cylindrical holes opening onto the molding surface S of the side plate 21, and the slits 26 are minute gaps opening onto the molding surface S of the side plate 21. Both of these discharge air remaining inside the mold 20 during vulcanization. The molding surface S of the side plate 21 has an outer region Ao located on the outer side in the tire radial direction and an inner region Ai located on the inner side in the tire radial direction, with the tire maximum width position Pmax as the boundary. The tire maximum width position Pmax is the position where the tire T has its maximum width in the rotational axis direction. In other words, it is the position where the distance between the molding surfaces S of the pair of side plates 21 in the tire rotational axis direction is greatest. The side plate 21 has at least one slit 26 in at least the outer region Ao (preferably in each of the outer region Ao and the inner region Ai), and the number S1 of the slits 26 arranged in the outer region Ao is greater than the number S2 of the slits 26 arranged in the inner region Ai. In other words, the number S1 of the slits 26 arranged in the outer region Ao and the number S2 of the slits 26 arranged in the inner region Ai satisfy the relationship S1>S2.

[0032] Unlike the cylindrical vent holes 25, these air-release slits 26 hardly allow rubber to flow into them, so spew, as occurs with vent holes 25, does not occur, and no spew cut marks Y (see FIG. 2) are left behind. Even if traces X (see FIG. 2) of the slits 26 are formed due to rubber flowing into the slits 26, only fine linear traces X remain, so the tire's appearance is not marred and the air resistance of the tire T is not adversely affected. Furthermore, the conventional process of cutting off spew after vulcanization is no longer necessary. Therefore, by replacing more vent holes 25 with slits 26, the effect of suppressing poor appearance and reducing air resistance can be improved.

[0033] In this way, in the tire molding mold 20, the molding surface S of the side plate 21 has an outer region Ao and an inner region Ai bounded by the tire maximum width position Pmax, and the side plate 21 has at least one air-vent slit 26 in at least the outer region Ao, so that air remaining between the tire T and the side plate 21 is discharged through the slit 26, thereby suppressing poor vulcanization, suppressing poor appearance of the tire T, and reducing the air resistance of the tire T. In particular, the number S1 of the slits 26 arranged in the outer region Ao, which has a relatively large effect on air resistance, is greater than the number S2 of the slits 26 arranged in the inner region Ai, so that the effect of reducing air resistance can be enhanced.

[0034] 5 and 6 each show an example of a side plate having a slit. As described above, the slit 26 is a minute gap at the opening. The width W of the slit 26 is preferably 0.01 mm to 0.5 mm, and more preferably 0.02 mm to 0.05 mm. By making the width W of the slit 26 sufficiently small, rubber does not substantially flow into the slit 26. Even if traces X of the slit 26 remain due to the rubber that has flowed into the slit 26, only minute linear traces X remain. This prevents damage to the tire's appearance and prevents poor appearance. If the width W of the slit 26 is less than 0.01 mm, it becomes difficult to ensure sufficient exhaust performance. Furthermore, the slit 26 is too thin, making it difficult to manufacture a mold (process the slit 26). If the width W of the slit 26 exceeds 0.5 mm, rubber easily flows into the slit 26, leaving traces X of the slit 26.

[0035] The length L of the slit 26 is preferably 0.6 mm to 13.0 mm, and more preferably 1.0 mm to 1.5 mm. By making the length L of the slit 26 sufficiently large, it is possible to reliably prevent the inflow of rubber while maintaining exhaust performance, thereby preventing the tire's appearance from being impaired and preventing poor appearance. If the length L of the slit 26 is less than 0.6 mm, it becomes difficult to ensure sufficient exhaust performance. If the length L of the slit 26 exceeds 13.0 mm, rubber is likely to flow into the slit 26. Furthermore, if traces X of the slit 26 remain, the effect of suppressing air resistance decreases. Furthermore, the ratio L / W of the length L of the slit 26 to the width W of the slit 26 is preferably 5 or more, and more preferably in the range of 10 to 100. By increasing the ratio L / W, it is possible to ensure good exhaust performance while preventing the inflow of rubber.

[0036] In the tire molding die 20, it is preferable that the number S1 of slits 26 arranged in the outer region Ao and the number V1 of cylindrical vent holes 25 arranged in the outer region Ao satisfy the relationship of 0.5 < S1 / (S1 + V1) ≤ 1.0, and the number S2 of slits 26 arranged in the inner region Ai and the number V2 of cylindrical vent holes 25 arranged in the inner region Ai satisfy the relationship of 0 < S2 / (S2 + V2) ≤ 0.5. Considering the improvement of appearance defects and the reduction of air resistance, it is desirable to increase the ratio of the number S1 of slits 26 arranged in the outer region Ao and the number S2 of slits 26 arranged in the inner region Ai. However, if the ratio becomes excessively high, the manufacturing man-hours of the slits 26 increase and the manufacturing efficiency of the die decreases. On the other hand, by relatively increasing the value of S1 / (S1 + V1) in the outer region Ao and relatively decreasing the value of S2 / (S2 + V2) in the inner region Ai, it is possible to realize the improvement of appearance defects and the reduction of air resistance while minimizing the decrease in die manufacturing efficiency. In particular, it is desirable that the number S1 of slits 26 arranged in the outer region Ao and the number V1 of cylindrical vent holes 25 arranged in the outer region Ao satisfy the relationship of 0.7 ≤ S1 / (S1 + V1) ≤ 0.8, and the number S2 of slits 26 arranged in the inner region Ai and the number V2 of cylindrical vent holes 25 arranged in the inner region Ai satisfy the relationship of 0.2 ≤ S2 / (S2 + V2) ≤ 0.3.

[0037] The slits 26 may be formed directly in the side plate 21 (see FIG. 5 ). Alternatively, as shown in FIG. 6 , the side plate 21 may have a replacement piece 28 with at least one slit 26 formed therein and a hole 29 into which the replacement piece 28 is inserted. The replacement piece 28 is a component that is detachably inserted into a hole 29 provided in the side plate 21, and when inserted into the hole 29, it constitutes a part of the molding surface S of the side plate 21. When the replacement piece 28 is inserted into the hole 29 in this manner, a slit 26 is formed between the side surface of the replacement piece 28 and the inner surface of the hole 28. Normally, when cleaning the mold 20, the cleaning work is performed with the mold 20 removed from the tire vulcanization apparatus. However, when a replacement piece 28 with a slit 26 formed therein is used, the molding surface, including the slit 26, can be cleaned by removing only the replacement piece 28 without removing the mold 20 from the tire vulcanization apparatus. This improves the workability when cleaning the mold 20 (particularly the side plate 21) after vulcanization. In order to fill the gap between the side plate 21 and the spare piece 28, it is desirable that the thermal expansion coefficient of the material constituting the spare piece 28 be higher than the thermal expansion coefficient of the material constituting the side plate 21.

[0038] The slit 26 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 28 as described above.

[0039] FIG. 7 shows a modified example of a tire mold. As shown in FIG. 7, the side plate 21 constituting the tire mold 20 has circumferential grooves 31 extending in the circumferential direction in addition to vent holes 25 and slits 26. The circumferential grooves 31 have a depth of 0.3 mm to 5.0 mm and a width of 0.1 mm to 5.0 mm. At least one of the slits 26 communicates with the circumferential grooves 31. When such circumferential grooves 31 are provided, air remaining between the tire T and the side plate 21 collects in the circumferential grooves 31 and is discharged to the outside of the mold 20 through the slits 26 communicating with the circumferential grooves 31. As a result, it is possible to reduce the number of slits 26 and vent holes 25 formed in the side plate 21, thereby reducing the number of steps required to manufacture the mold. Note that, because transfer marks of the circumferential grooves 31 are formed in the sidewall portion 2 of the tire T, it is desirable to arrange the circumferential grooves 31 in an inner region Ai where the effect on air resistance is relatively small.

[0040] 7, the side plate 21 constituting the tire molding mold 20 has a radial groove 32 extending radially across the tire maximum width position Pmax. The radial groove 32 has a depth of 0.3 mm to 5.0 mm and a width of 0.1 mm to 5.0 mm. An end of the radial groove 32 in the outer region Ao communicates with one of the slits 26, and an end of the radial groove 32 in the inner region Ai communicates with a cylindrical vent hole 25. When such a radial groove 32 is provided, air remaining between the tire T and the side plate 21 collects in the radial groove 32 and is discharged to the outside of the mold 20 through the vent hole 25 and slit 26 that communicate with the radial groove 32. As a result, it is possible to reduce the number of slits 26 and vent holes 25 formed in the side plate 21, thereby reducing the number of steps required for mold production. In this case, since the slits 26 are connected to the ends of the radial grooves 32 in the outer region Ao, an increase in air resistance due to the traces X of the slits 26 can be suppressed, and air resistance can be effectively reduced.

[0041] When manufacturing a tire T using the tire mold 20 described above, an unvulcanized tire T is molded and then vulcanized in the tire mold 20. At this time, air is removed from the mold 20 through the vent holes 25 and the slits 26. Although a spew is formed in the vent holes 25 due to the inflow of rubber, the slits 26 are tiny gaps through which almost no rubber flows. As a result, in the tire T after vulcanization, almost no trace X resulting from air removal is formed on the surface of the sidewall portion 2 (the portion where air is removed using the slits 26). Even if trace X of the slit 26 is formed due to rubber flowing into the slit 26, only a linear trace X with a fine width remains in a portion. Even if trace X of the slit 26 is formed, since it is a linear trace with a fine width, it is not easily visible, and the trace X of the slit 26 does not detract from the appearance of the sidewall portion 2. Furthermore, the trace X of the slit 26 does not impair the air resistance of the tire T. Therefore, by replacing more vent holes 25 with slits 26, the above-mentioned effect can be enhanced.

[0042] The tire T manufactured using the tire mold 20 described above is recognized as having minute traces X of the slits 26 on the surface of the sidewall portion 2. Such a tire T has few vulcanization defects, has a good appearance as a tire product at the shipping stage, and also has low air resistance. The tire T may have spew cut marks Y caused by the vent holes 25 on the surface of the sidewall portion 2. By replacing more vent holes 25 with slits 26, it is possible to reduce the spew cut marks Y. [Example]

[0043] In manufacturing a tire with a tire size of 165 / 50R16 75V, the molding surface of the side plate constituting the tire molding mold was defined into an outer region and an inner region, with the boundary being the maximum tire width position, and vent holes or slits were provided in the side plate as an exhaust mechanism. The relationship between the number of slits S1 arranged in the outer region and the number of slits S2 arranged in the inner region, the diameter of the vent hole, the width of the slit, the length of the slit, the presence or absence of circumferential grooves, the presence or absence of radial grooves, the ratio [S1 / (S1+V1)] of the number of slits S1 to the sum of the number of slits S2 arranged in the outer region and the number of vent holes V1 arranged in the outer region, the ratio [S2 / (S2+V2)] of the number of slits S2 arranged in the inner region and the sum of the number of vent holes V2 arranged in the inner region, and the method of forming the exhaust mechanism were set as shown in Table 1 (Conventional Example and Examples 1 to 9).

[0044] Regarding the "method of forming the exhaust mechanism," the case where the exhaust mechanism (slits, vent holes) was directly formed in the side plate was indicated as "directly formed," and the case where a replacement piece with the exhaust mechanism formed was used was indicated as "replacement piece." Also, when a circumferential groove was formed, the circumferential groove was positioned in the inner region of the side plate.

[0045] These conventional examples and Examples 1 to 9 were evaluated for productivity, appearance, low air resistance, cleaning workability, and mold processability using the following evaluation methods. The results are also shown in Table 1.

[0046] Productivity: 1,000 tires were vulcanized using each tire molding mold, and the tires were visually inspected immediately after vulcanization. The number of tires with vulcanization defects due to poor exhaust was counted to determine the rate of vulcanization defects. The evaluation results were expressed as an index using the reciprocal of the rate of vulcanization defects, with the conventional example being set at 100. The higher the index value, the fewer tires with vulcanization defects, indicating better productivity.

[0047] Appearance: For tires that did not show any vulcanization defects in the above-mentioned productivity evaluation, the spews were cut off and other work was carried out to return them to the state they were in at the time of shipment. These tires were then visually inspected and subjected to a sensory evaluation for any defects in appearance (such as deterioration in appearance due to cut marks on the spews). The evaluation results were expressed as an index, with the conventional example being set at 100. The higher the index value, the better the appearance.

[0048] Low air resistance: The pneumatic tires manufactured using each tire molding mold were mounted on wheels with a rim size of 16 x 5.0J, the air pressure was adjusted to 230 kPa, and the tires were then mounted on a test vehicle. In accordance with JIS D1012, the vehicle speed while coasting was measured and the running resistance was calculated using the multi-point regression method. The evaluation results were expressed as an index using the reciprocal of the measured value, with the conventional example being set at 100. The higher the index value, the lower the air resistance.

[0049] Cleaning 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 the conventional example being set at 100. The higher the index value, the shorter the time required to clean the mold and the better the cleaning workability.

[0050] Mold processability: The time required to process the vent holes and slits for each tire mold was measured. The evaluation results were expressed as an index using the reciprocal of the measured value, with the conventional example being set at 100. The higher the index value, the better the mold processability.

[0051] [Table 1]

[0052] As can be seen from Table 1, in comparison with the conventional example in which only a vent hole was provided in the side plate as an exhaust mechanism, Examples 1 to 9 were able to improve appearance and low air resistance while maintaining good productivity (exhaust performance), and also had good cleaning workability.

[0053] The present disclosure includes the following inventions [1] to

[10] . Invention [1] is a tire molding mold for molding a tire, comprising side plates for molding the sidewall portion of the tire, the molding surface of the side plates having outer and inner regions bounded by the maximum tire width position, the side plates having at least one air-bleeding slit in at least the outer region, and the number S1 of slits arranged in the outer region being greater than the number S2 of slits arranged in the inner region. Invention [2] is the tire molding mold according to invention [1], characterized in that the side plate has at least one air-bleeding slit in each of the outer region and the inner region. Invention [3] is the tire mold according to invention [1] or [2], characterized in that the width of the slit is 0.01 mm to 0.5 mm. Invention [4] is the tire mold according to any one of inventions [1] to [3], characterized in that the length of the slit is 0.6 mm to 13.0 mm. Invention [5] is a tire molding mold according to any one of Inventions [1] to [4], characterized in that the side plate has a circumferential groove extending in the circumferential direction and having a depth of 0.3 mm to 5.0 mm and a width of 0.1 mm to 5.0 mm, and at least one of the slits communicates with the circumferential groove. Invention [6] is a tire molding mold according to any one of Inventions [1] to [5], characterized in that the side plate has a radial groove extending radially across the maximum width position of the tire and having a depth of 0.3 mm to 5.0 mm and a width of 0.1 mm to 5.0 mm, and one of the slits communicates with an end of the radial groove in the outer region, and a cylindrical vent hole communicates with an end of the radial groove in the inner region. The invention [7] is the tire molding die according to any one of inventions [1] to [6], characterized in that the number S1 of slits arranged in the outer region and the number V1 of cylindrical vent holes arranged in the outer region satisfy the relationship of 0.5 < S1 / (S1 + V1) ≤ 1.0, and the number S2 of slits arranged in the inner region and the number V2 of cylindrical vent holes arranged in the inner region satisfy the relationship of 0 < S2 / (S2 + V2) ≤ 0.5. The invention [8] is the tire molding die according to any one of inventions [1] to [7], characterized in that the side plate has a replacement piece in which at least one of the slits is formed and a hole portion into which the replacement piece is inserted. The invention [9] is a method for manufacturing a tire using the tire molding die according to any one of inventions [1] to [8], characterized in that an unvulcanized tire is put into the tire molding die, and while performing air venting through the slits, the unvulcanized tire is vulcanized in the tire molding die. The invention

[10] is a tire manufactured by the method for manufacturing a tire according to the invention [9], characterized in that the surface of the sidewall portion has traces of the slits.

Explanation of Signs

[0054] 1 Tread portion 2 Sidewall portion 3 Bead portion 20 Mold 21 Side plate 22 Bead ring 23 Sector 25 Vent hole 26 Slit 27 Vent passage 28 Replacement piece 29 Hole portion 30 Bladder 31 Circumferential groove 32 Radial groove

Claims

1. A tire molding mold for molding a tire, comprising: side plates for molding sidewall portions of the tire; a molding surface of the side plate having an outer region and an inner region bordered by a maximum tire width position; the side plate having at least one air-bleeding slit in at least the outer region; and a number S1 of slits arranged in the outer region being greater than a number S2 of slits arranged in the inner region.

2. 2. The tire mold according to claim 1, wherein the side plate has at least one slit for venting air in each of the outer and inner regions.

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

4. 2. The tire mold according to claim 1, wherein the length of the slit is 0.6 mm to 13.0 mm.

5. The tire mold according to claim 1, characterized in that the side plate has a circumferential groove extending in the circumferential direction and having a depth of 0.3 mm to 5.0 mm and a width of 0.1 mm to 5.0 mm, and at least one of the slits communicates with the circumferential groove.

6. 2. The tire mold according to claim 1, wherein the side plate has a radial groove that extends radially across the tire maximum width position and has a depth of 0.3 mm to 5.0 mm and a width of 0.1 mm to 5.0 mm, and wherein an end of the radial groove in the outer region communicates with one of the slits, and an end of the radial groove in the inner region communicates with a cylindrical vent hole.

7. 2. The tire mold according to claim 1, wherein the number S1 of slits arranged in the outer region and the number V1 of cylindrical vent holes arranged in the outer region satisfy the relationship 0.5 < S1 / (S1 + V1) ≦ 1.0, and the number S2 of slits arranged in the inner region and the number V2 of cylindrical vent holes arranged in the inner region satisfy the relationship 0 < S2 / (S2 + V2) ≦ 0.

5.

8. 2. The tire mold according to claim 1, wherein the side plate has a replacement piece in which at least one of the slits is formed, and a hole into which the replacement piece is inserted.

9. A tire manufacturing method using the tire molding mold according to any one of claims 1 to 8, 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.

10. A tire manufactured by the tire manufacturing method according to claim 9, characterized in that the surface of the sidewall portion has traces of the slits.

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