JP5216110B2 - Tire vulcanization mold - Google Patents

Description

  The present invention relates to a vulcanization mold for a tire that helps to reduce vulcanization defects such as bears on a bead heel surface of a bead portion by improving the structure of a bead ring.

  As shown in FIG. 9 (a), the tire vulcanization mold m forms a tread molding part ma for molding the tread part, a sidewall molding part mb for molding the sidewall part, and a bead part b. And a removable bead ring mc. As shown in FIG. 9 (b), the bead ring mc includes a bead bottom molding surface g1 for molding the bead bottom surface b1 of the tire bead portion b, and a heel molding surface g2 for molding the bead heel surface b2 of the bead portion b. The bead forming surface g is formed including an outer molding surface g3 for molding the tire axial direction outer surface b3 of the bead portion b.

  By the way, the bead molding surface g is bent in an L shape at the bead heel surface b2 as shown in FIG. 9B. Therefore, at the time of vulcanization molding, the rubber in the bead part b comes into contact with the bead bottom molding surface g1 and the outer molding surface g3 first, and air is trapped between the bead part b and the heel molding surface b2, The accumulation e is likely to occur, and this tends to cause poor vulcanization (dent) called a bear in the molded tire.

  As a method for preventing the air accumulation e, it is known to provide a vent hole (not shown) for exhaust in the mold. However, since the vent hole is processed using a tool such as a drill, it is difficult to form the bent hole on the curved heel molding surface g2 having a small curvature radius. In addition, when a vent hole is provided, part of the rubber is sucked together with the air, so that a beard-like protrusion called a spew is formed on the bead portion after vulcanization, and the work for cutting off the spew is performed. It takes time and effort. In addition, since some protrusions remain even after excision, there is a problem in that these protrusions adversely affect the fitting property with the rim. Documents related to such technology include the following.

JP 11-138547 A JP 2000-52347 A

  The present invention has been devised in view of the above problems, and by improving the structure of the bead ring, the air remaining on the bead heel surface of the bead portion is discharged during vulcanization and the generation of bears and the like. The main objective is to provide a tire vulcanization mold that helps to reduce tires.

The invention according to claim 1 of the present invention comprises a bead bottom molding surface for molding a bead bottom surface of a bead portion of a tire, a heel molding surface for molding a bead heel surface of a bead portion, and a tire axial direction outer surface of the bead portion. A tire vulcanization mold including a bead ring having a bead molding surface composed of an outer molding surface to be molded,
The bead ring is formed of two or more ring pieces that are divided inward and outward in the tire axial direction by one or more divided surfaces extending from the bead heel surface, and on the divided surface of one ring piece adjacent to the divided surface. A plurality of circumferential grooves extending in the circumferential direction, and extending from the circumferential groove to the bead heel surface and forming an exhaust slit having a gap G of 0.02 to 0.08 mm between the other ring piece split surface. The circumferential groove is formed from a plurality of circumferential grooves arranged at intervals in the circumferential direction, and the plurality of slit forming grooves are connected to each circumferential groove. , Bentoho the one side, the outer ring pieces arranged in the tire axial direction outer side of the other side of the ring piece, the and end extends through the outer side of the ring piece communicating with said circumferential groove Characterized in that a Le.

According to a second aspect of the present invention, in the tire vulcanization mold according to the first aspect, an angle in the tire circumferential direction of the circumferential groove portion is 10 to 40 degrees .

  In the invention according to claim 3, the bead ring is divided into three ring pieces inside, inside and outside in the tire axial direction by two dividing surfaces, and the vent hole penetrating the inside ring piece is: One end communicates with a circumferential groove formed on the dividing surface between the inner and inner ring pieces, and the other end communicates with a circumferential groove formed on the dividing surface between the inner and outer ring pieces. The tire vulcanization mold according to claim 1 or 2.

  According to a fourth aspect of the present invention, the vent hole penetrating the outer ring piece has one end communicating with a circumferential groove formed in a split surface between the inner ring pieces and the other end being a bead ring. The tire vulcanization mold according to claim 3, wherein the tire vulcanization mold is electrically connected to the outside.

  The tire vulcanization mold of the present invention includes a bead ring having a bead molding surface. The bead ring is formed of two or more ring pieces divided inward and outward in the tire axial direction by one or more division surfaces extending from the bead heel surface, and on the division surface of one ring piece adjacent to the division surface, A circumferential groove extending in the circumferential direction and a slit forming groove extending from the circumferential groove to the bead heel surface are provided. Further, a vent hole extending through the outer ring piece and having one end communicating with the circumferential groove is provided in the outer ring piece arranged on the outer side in the tire axial direction. Thus, during vulcanization molding, air remaining between the bead portion and the heel molding surface of the bead ring can be reliably discharged to the outside from the slit forming groove and the circumferential groove through the vent hole. In addition, in the vicinity of the bead portion, a plurality of slit forming grooves that form an exhaust slit with a gap G of 0.02 to 0.08 mm are arranged between the ring piece on one side and the split surface of the ring piece on the other side. Therefore, the sucking of rubber is suppressed and the formation of spew is reduced. Therefore, the pneumatic tire produced by the tire vulcanization mold of the present invention is excellent in aesthetics.

It is sectional drawing of the pneumatic tire obtained with the manufacturing method of this invention. It is sectional drawing of the shaping | molding apparatus of the tire containing the vulcanization metal mold | die of this embodiment. It is sectional drawing explaining a bead ring. (A) is a perspective view of a bead ring, (b) is a perspective view of each ring piece. (A) is an inner ring piece, (b) is an inner ring piece, and (c) is an enlarged partial perspective view of an outer ring piece. (A) is sectional drawing explaining the process of shape | molding a raw cover, (b) is sectional drawing explaining the vulcanization | cure process which vulcanizes a raw cover. It is sectional drawing which shows the manufacturing apparatus of the pneumatic tire of other embodiment. (A) is a ring piece in another embodiment, (b) is a ring piece in another embodiment, and (c) is an enlarged partial perspective view of an outer ring piece in another embodiment. is there. (A) is sectional drawing of the conventional vulcanization metal mold | die, (b) is a cross-sectional schematic diagram which shows the contact state of the bead molding surface and bead part of the vulcanization metal mold | die of (a).

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
In FIG. 1, sectional drawing of the pneumatic tire 1 manufactured using the vulcanization die of the tire of this embodiment is shown. The pneumatic tire 1 includes a carcass 6 extending from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4, and a belt layer 7 disposed on the outer side in the tire radial direction of the carcass 6 and inside the tread portion 2. For passenger cars including

  The carcass 6 includes a carcass ply 6 </ b> A having a carcass cord extending from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4. In the carcass ply 6A, carcass cords made of, for example, organic fibers are arranged at an angle of, for example, 75 to 90 ° with respect to the tire equator C direction. The carcass ply 6 </ b> A of the present embodiment straddles between the bead portions 4, 4 in a toroidal shape, and end portions 6 e on both sides thereof are terminated in the bead core 5 without being folded back by the bead core 5. An inner liner 8 made of rubber having excellent air impermeability is disposed inside the carcass 6.

  The belt layer 7 is composed of at least two belt plies 7A and 7B, in the present embodiment, in the tire radial direction, and in the outer two. Each of the belt plies 7A and 7B has a highly elastic belt cord such as a steel cord inclined at an angle of 15 to 40 ° with respect to the tire equator C. The belt plies 7A and 7B are overlapped so that the belt cords cross each other.

  In this embodiment, the bead core 5 includes an inner core piece 5i disposed on the inner side in the tire axial direction of the carcass ply 6A and an outer core piece 5o disposed on the outer side in the tire axial direction of the carcass ply 6A. Prepare. The end 6e of the carcass ply 6A is held between the inner and outer core pieces 5i and 5o. A clinch rubber 4G made of hard rubber is disposed on the inner side in the tire radial direction of the bead core 5 in order to prevent wear due to contact with a rim (not shown).

  FIG. 2 shows an embodiment of a molding apparatus 10 for vulcanizing and molding the pneumatic tire 1. The molding apparatus 10 includes a vulcanization mold M of the present embodiment and, for example, a hard core N disposed in a cavity of the vulcanization mold M. In FIG. 2, the vulcanization mold M is completely closed. Thereby, a molding space k for vulcanizing and molding the pneumatic tire 1 is formed between the vulcanizing mold M and the core N.

  The core N is, for example, an assembly type that becomes an annular body substantially continuous in the tire circumferential direction by assembling segments divided in the tire circumferential direction. Further, since the core N is disposed in the vulcanization mold M, the core N is made of a metal material, heat-resistant resin, or the like that can withstand heat and pressure during vulcanization. The inside of the core N is hollowed out, and a heater or the like (not shown) for heating the raw cover from the inside can be incorporated in the space.

  In addition, the core N has a molding surface 9 that forms the inner cavity surface i of the pneumatic tire 1. The molding surface 9 includes a tread lumen molding surface 9 a that molds the lumen surface 2 i of the tread portion 2, a sidewall portion lumen molding surface 9 b that molds the lumen surface 3 i of the sidewall portion 3, and the bead portion 4. A bead lumen forming surface 9c for forming the tire lumen surface 4i.

  The core N includes a core main body 12 constituting a main part of the core N, and an exchangeable ring-shaped and rectangular cross-sectional attachment piece 13 constituting a part of the bead lumen forming surface 9c. It is desirable to include it. Such an attachment piece 13 is particularly suitable for efficiently performing maintenance of the inner portion in the tire radial direction of the bead lumen forming surface 9c, which is particularly worn.

  As shown in FIG. 2, the vulcanization mold M includes an outer surface of the sidewall portion 3 and a tread ring M1 capable of expanding and contracting, for example, forming the outer surface of the tread portion 2 of the raw cover 1a (pneumatic tire). It includes a pair of side rings M2 that are molded and movable in the tire axial direction, and a pair of bead rings M3 that mold at least the bottom surface of the bead portion 4 and are movable in the tire axial direction.

  The tread ring M1 and the side ring M2 can adopt the same configuration as the conventional one.

  As shown in FIGS. 3 and 4, the bead ring M3 of the present embodiment has a ring shape continuous in the tire circumferential direction, and forms a bead bottom 4a (shown in FIG. 2) of the bead portion 4 of the tire. A molding surface 14, an arc-shaped heel molding surface 15 that is continuous with the heel side of the bead bottom molding surface 14 and molds a bead heel surface 4 b (shown in FIG. 2) of the bead portion 4, and a tire radius of the heel molding surface 15 A bead molding surface 17 is formed which is connected to the outer side in the direction and includes an outer molding surface 16 for molding the tire axial direction outer surface 4c (shown in FIG. 2) of the bead portion 4. The bead ring M3 is connected to the inner end 17e in the tire axial direction of the bead molding surface 17 and is connected to the inner surface in the tire radial direction of the attachment piece 13 (shown in FIG. 2). And an inner forming surface 19 connected to the inner end 18e in the tire axial direction and extending inward in the tire radial direction.

  The bead ring M3 is formed of two or more ring pieces R that are divided inward and outward in the tire axial direction by one or more divided surfaces S extending from the bead heel surface 4b. The bead ring M3 according to the present embodiment is formed in the tire axial direction by two divided surfaces, an inner divided surface S1 disposed on the inner side in the tire axial direction and an outer divided surface S2 disposed on the outer side in the tire axial direction with respect to the inner divided surface S1. It is formed from three inner, outer and inner ring pieces 20, 21 and 22 which are divided into inner and outer. That is, in the present embodiment, the inner divided surface S1 is formed by an inner / inner divided area 20a on the outer side in the tire axial direction of the inner ring piece 20 and an inner / inner divided area 21a on the inner side in the tire axial direction of the inner ring piece 21. Is done. Similarly, the outer divided surface S2 is formed of an inner / outer divided region 21b on the outer side in the tire axial direction of the inner ring piece 21 and an outer / inner divided region 22a on the inner side in the tire axial direction of the outer ring piece 22. In the present embodiment, the inner and outer three ring pieces 20, 21, 22 are fixed to the three ring pieces as a single unit. There are four places in the direction.

  Further, in the present embodiment, the inner and middle divided regions 20a of the inner ring piece 20 include a bead heel surface 4b, that is, an inner inclined surface 23 extending from the heel molding surface 15 to the tire axial direction outer side and the tire radial direction inner side, The inner inclined surface 23 extends from the outer end 23e in the tire axial direction to the inner side in the tire radial direction, and the inner and outer surface 24 extends from the inner end 24e in the tire radial direction to the inner side in the tire radial direction and in the tire axial direction. An inner inner surface 25 that terminates in the inner forming surface 19 is formed. Similarly, the inner and outer divided regions 21b of the inner ring piece 21 have an intermediate inclined surface 28 that extends from the heel molding surface 15 in the tire axial direction outer side and the tire radial direction inner side, and the intermediate inclined surface 28 in the tire axial direction. An inner outer surface 29 extending inward in the tire radial direction from the outer end 28e, and an inner inner surface extending from the inner end 29e in the tire radial direction of the inner outer surface 29 in the tire radial direction and in the tire axial direction and terminating at the inner forming surface 19 30.

  Further, the outer surface in the tire axial direction of the outer ring piece 22 of the present embodiment is an inclined surface extending from the outer end 16e in the tire radial direction of the outer molding surface 16 inwardly in the tire radial direction and outward in the tire axial direction. 31 and an outer surface 32 extending from the outer end 31e in the tire axial direction of the inclined surface 31 to the inner side in the tire radial direction.

  In the present invention, the circumferential groove 26 extending in the circumferential direction on the divided surface of one ring piece adjacent on the divided surface S, and a plurality of slit forming grooves extending from the circumferential groove 26 to the bead heel surface 4b. 27 is provided.

  The circumferential groove 26 includes an inner circumferential groove 26a formed on the inner divided surface S1 and an outer circumferential groove 26b formed on the outer divided surface S2. In the present embodiment, the inner circumferential groove 26 a is disposed in contact with the tire radial inner edge 23 i of the inner inclined surface 23 of the inner ring piece 20 and on the outer side in the tire radial direction of the inner and outer surfaces 24. Further, in the present embodiment, the outer circumferential groove 26b is disposed in contact with the tire radial inner edge 28i of the middle inclined surface 28 of the inner ring piece 21 and on the outer side in the tire radial direction of the middle outer surface 29.

  Further, as shown in FIG. 4B, the inner and outer circumferential grooves 26a and 26b are arranged at intervals in the circumferential direction in the present embodiment, for example, a plurality of circumferential directions having a substantially arc shape. It is formed from the groove part 26c.

  When the number of the circumferential grooves 26c is increased, the rigidity of the ring pieces 20 and 21 may be lowered and the durability may be deteriorated. There is a risk that it cannot be discharged well. From such a viewpoint, the number of the circumferential groove portions 26c disposed is preferably 8 to 20, more preferably 10 to 15 on the tire circumference. From the same viewpoint, the tire circumferential angle θ1 representing the size of the circumferential groove 26c is preferably 10 to 40 degrees, more preferably 15 to 35 degrees. Further, from the same viewpoint, the groove depth t (shown in FIG. 3) of the circumferential groove 26c is preferably 0.8 to 2.2 mm, more preferably 1.0 to 2.0 mm.

  The slit forming groove 27 is formed as an exhaust slit having a gap G of 0.02 to 0.08 mm between the split surface of the ring piece on one side and the split surface of the ring piece on the other side.

  4 (b), 5 (a), and 5 (b), the slit forming groove 27 of the present embodiment extends the inner inclined surface 23 of the inner ring piece 20 in and out of the tire axial direction. An inner slit forming groove 27a continuous with the inner circumferential groove 26a, and an inner slit forming groove 27b extending the inner inclined surface 28 of the inner ring piece 21 in and out of the tire axial direction and connected to the outer circumferential groove 26b. Become.

  In addition, the slit forming groove 27 of the present embodiment is disposed at the same interval in the tire circumferential direction from the circumferential groove portion 26c. Moreover, although the cross section of the slit formation groove | channel 27 is formed in a substantially rectangular shape, it is not limited to such an aspect, For example, a substantially U shape, a substantially triangular shape, etc. may be sufficient.

  When the gap G is small, the slit forming groove 27 cannot suppress the generation of bears since air is not discharged during tire vulcanization. On the other hand, if the gap G is large, the rubber of the raw cover 1a flows into the slit forming groove 27 and causes spew. From such a viewpoint, the upper limit of the gap G (shown in FIG. 3) is preferably 0.06 mm or less, more preferably 0.04 mm or less.

  Further, the number of the slit forming grooves 27 is desirably about 200 to 400 on the tire circumference in order to efficiently discharge the air remaining at the time of vulcanization.

  Further, in the present invention, the outer ring piece disposed on the outer side in the tire axial direction of the one side ring ring side and the other side ring piece extends through the outer ring piece and one end thereof is the circumferential groove 26. A vent hole B communicating with is provided.

  In the present embodiment, the vent hole B includes an inner vent hole B1 that penetrates the inner ring piece 21 and an outer vent hole B2 that penetrates the outer ring piece 22.

  The vent hole B1 in the present embodiment has one end communicating with the inner circumferential groove 26a formed on the split surface S1 between the inner and inner ring pieces 20, 21, and the other end being the middle. It communicates with the outer circumferential groove 26b formed in the dividing surface S2 between the outer ring pieces 21 and 22.

  The outer vent hole B2 has one end communicating with the outer circumferential groove 26b formed in the split surface S2 between the inner and outer ring pieces 21 and 22, and the other end conducting outside the bead ring. .

  The inclined surface 31 of the outer ring piece 22 of the present embodiment has a plurality of slit-shaped grooves that terminate from the outer end 16e outward in the tire axial direction without reaching the outer end 31e of the inclined surface 31. 33 and a groove 34 that extends to the slit forming groove 27 and extends beyond the inner end P (shown in FIG. 2) of the side ring M2 in the tire radial direction. Then, the other end of the outer vent hole B2 communicates with the groove 34, so that the outer vent hole B2 conducts outside the bead ring.

  The diameter d of the vent hole B is preferably 1 from the viewpoint of reliably discharging the air accumulated in the circumferential groove 26 from the slit forming groove 27 and ensuring the durability of the ring pieces 21 and 22. 0.5 to 4.5 mm is desirable, and 2.0 to 4.0 mm is more desirable.

  A method for manufacturing the pneumatic tire 1 using the molding apparatus 10 including the vulcanizing mold M configured as described above will be described. The manufacturing method of the present embodiment includes a step of forming the raw cover 1a and a vulcanization step of vulcanizing the raw cover 1a.

  For example, as shown in FIG. 6A, the raw cover 1 a is molded by attaching a tire constituent member to the molding surface 9 of the core N. In the present embodiment, the inner liner 8, the base portion 4Ga of the clinch rubber 4G on the tire axial direction inner side, the bottom portion 4Gb of the clinch rubber 4G, the inner core piece 5i, the carcass ply 6A, the outer core piece 5o, and the clinch rubber 4G outer side in the tire axial direction. The base 4Gc, the side wall rubber 3G, the belt plies 7A and 7B, and the tread rubber 2G are attached in this order. However, the pasting order and shape of each member are not limited to such an aspect.

  Next, a vulcanization process for vulcanizing the raw cover 1a is performed. In the vulcanization step, the vulcanization mold M is opened, and the raw cover 1a is put together with the core N into the molding space k (shown in FIG. 2). 6B, the bead ring M3, the side ring M2, and the tread ring M1 are closed, and the vulcanizing mold M and / or the core N are heated, whereby the raw cover 1a is vulcanized. Molded. Due to the expansion of the rubber material of the raw cover 1a with respect to the molding space k, the air remaining in the molding space k, particularly between the bead ring M3 and the bead portion 4, enters the slit forming groove 27.

  When the vulcanization is completed, the vulcanization mold M is opened, and the pneumatic tire 1 is taken out together with the core N from the molding space k. Further, the core N is disassembled and removed from the inside of the pneumatic tire 1.

  In this vulcanization step, since the air remaining from the slit forming groove 27 to the vent hole B through the circumferential groove 26 is discharged, the pneumatic tire 1 manufactured by the vulcanization mold M of this embodiment is used. The bead part 4 does not generate a bear. Furthermore, since the gap G of the slit forming groove 27 extending from the bead heel surface 4b is regulated to 0.02 to 0.08 mm, the inflow of rubber into the slit forming groove 27 is suppressed, and the occurrence of spew is prevented. Moreover, air can be discharged more effectively by setting the groove depth t of the circumferential groove 26 and the diameter d of the vent hole B to the above-described numerical ranges. Therefore, the pneumatic tire formed by the vulcanization mold M of the present invention is excellent in aesthetics.

FIG. 7 shows another method for manufacturing a pneumatic tire 1 of the present invention and a molding apparatus 11.
The molding surface 9 of the core N1 of this embodiment consists only of a bead lumen molding surface 9c that molds the tire lumen surface 4i of the bead portion 4 of the pneumatic tire 1, and the other part of the lumen surface i is: Vulcanization molding is performed using a bladder Bu made of a crosslinked rubber. Other parts are the same as those in the above embodiment. Accordingly, even in such an embodiment, since the air is reliably discharged, a pneumatic tire excellent in aesthetic appearance is produced without generating a bear in the bead portion 4.

  As mentioned above, although the especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect. For example, as shown in FIGS. 8A to 8C, the slit forming groove 27, the slit forming groove 33, the circumferential groove 26, and the groove portion 34 have a shape that continuously extends in the tire circumferential direction. But you can. Further, in order to ensure higher rigidity of the bead ring M3, the length in the tire radial direction of the circumferential groove 26 and the groove portion 34 is smaller than the length in the tire radial direction of the present embodiment shown in FIG. It doesn't matter.

In order to confirm the effect of the present invention, 100 radial radial tires for passenger cars of size 215 / 45R17 were manufactured according to the specifications shown in Table 1, and the appearance of the bead heel surface of the bead portion was examined. The parts other than those described in the table were the same. The main common specifications are as follows.
<Slit forming groove>
Number of arrangement: 300 on the tire circumference <circumferential groove>
Number of arrangement: 12 on the tire circumference Circumferential angle θ1: 20 degrees

The aesthetic appearance of the bead heel surface was determined in five stages using the following criteria by visual inspection and palpation by an inspector. The larger the value, the better.
5: No occurrence of bears and spews 4: Slight occurrence of bears and spews, but acceptable level without repair 3-2: Bears and spews, etc. that need repair are generated 1: Repair Table 1 shows the results of the test where an impossible bear occurred.

  As a result of the test, it was confirmed that the examples were less likely to generate bears and spews than the comparative example, and the aesthetic appearance was improved. In addition, when the groove depth of the circumferential groove was increased, the durability of the bead ring tended to deteriorate.

4 Bead portion 4a Bead bottom surface 4b Bead heel surface 4c Tire axial direction outer surface 14 Bead bottom molding surface 15 Heel molding surface 16 Outer molding surface 17 Bead molding surface 26 Circumferential groove 27 Slit forming groove B Vent hole E Exhaust slit M Vulcanized gold Type M3 Bead ring R Ring piece S Split surface

Claims (4)

A bead molding surface comprising a bead bottom molding surface that molds a bead bottom surface of a tire bead portion, a heel molding surface that molds a bead heel surface of the bead portion, and an outer molding surface that molds the tire axial direction outer surface of the bead portion. A tire vulcanization mold including a bead ring having,
The bead ring is formed of two or more ring pieces that are divided inward and outward in the tire axial direction by one or more dividing surfaces extending from the bead heel surface.
Moreover, between the circumferential groove extending in the circumferential direction on the divided surface of the ring piece on one side adjacent to the divided surface, and extending from the circumferential groove to the bead heel surface and between the divided surface of the other ring piece. The gap G includes a plurality of slit forming grooves that form an exhaust slit having a diameter of 0.02 to 0.08 mm, and
The circumferential groove is formed from a plurality of circumferential groove portions arranged at intervals in the circumferential direction, and the plurality of slit forming grooves are connected to each circumferential groove portion,
A vent hole extending through the outer ring piece and having one end communicating with the circumferential groove is provided in an outer ring piece arranged on the outer side in the tire axial direction of the ring pieces on the one side and the other side. A tire vulcanization mold characterized by that. The tire vulcanization mold according to claim 1, wherein an angle in a tire circumferential direction of the circumferential groove portion is 10 to 40 degrees . The bead ring is divided into three ring pieces inside, inside, and outside in the tire axial direction by two dividing surfaces,
One end of the vent hole that penetrates the inner ring piece communicates with a circumferential groove formed in a dividing surface between the inner and inner ring pieces, and the other end is divided between the inner and outer ring pieces. The tire vulcanization mold according to claim 1, wherein the tire vulcanization mold communicates with a circumferential groove formed on the surface.   The vent hole that penetrates the outer ring piece has one end communicating with a circumferential groove formed in a dividing surface between the inner ring pieces and the other end conducting to the outside of the bead ring. The tire vulcanization mold according to claim 3.

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