JP5010017B2 - Pneumatic tire manufacturing method and molding apparatus - Google Patents

Description

  The present invention relates to a method and apparatus for manufacturing a pneumatic tire with improved uniformity by improving the shape of a core and a bead ring.

  As shown in FIG. 9 (a) and FIG. 9 (b), which is an enlarged view of the part A, conventionally, a pneumatic tire vulcanizing method using a split mold m and a bladder b is known. Various types of the split mold m are known. For example, the outer surface of the tread ring m1 that forms the outer surface of the tread portion T of the raw cover g (pneumatic tire) and the outer surface of the sidewall portion S are formed. There are known ones including a pair of side rings m2 and a pair of bead rings m3 for forming the outer surface of the bead portion B.

  As shown in FIG. 9B, the bead ring m3 includes a bead bottom molding surface d1 that forms a bottom surface B1 that is an inner surface in the tire radial direction of the bead portion B, and an outer surface B2 of the bead portion B in the tire axial direction. And a bead outer surface forming surface d2 that are connected to each other via a smooth arc. Further, the bead ring m3 has a vertical surface d3 extending straight from the inner end d1e in the tire axial direction of the bead bottom molding surface d1 to the inside in the tire radial direction.

  In the molding apparatus, the split mold m is opened, the raw cover g is inserted into the cavity c, and then the split mold m is closed. A high pressure fluid is supplied to the bladder b charged in the split mold m. Thereby, as shown in FIG. 9A, the bladder b expands inside the raw cover g and presses the raw cover g against each molding surface of the split mold m. The raw cover g is subjected to the action of heat and pressure, and the plasticized rubber is vulcanized and molded into the inverted shape of the molding surface of the split mold m.

  Documents related to such technology include the following.

JP 2007-160699 A

  By the way, during vulcanization molding, the rubber that has been plasticized and has increased fluidity flows to the side with less resistance. For example, in the previous example, a part of the surplus rubber near the toe side of the bead portion B flows into a minute gap between the vertical surface d3 of the bead ring m3 and the bladder b. Then, after the vulcanization molding, the surplus rubber that has flowed into the gap and cured is burr p1 extending from the bottom surface B1 of the bead portion B in the tire radial direction as shown in FIG. Sometimes called "Long Toe").

  Since such a burr p1 is irregular in the generation position and the shape thereof, the inner diameter of the bottom surface B1 of the bead portion B is varied, and the uniformity of the tire is deteriorated. Of course, such a burr p1 is removed before shipment, but it is difficult to completely remove it.

  The present invention has been devised in view of the above problems, and is a pneumatic tire capable of improving uniformity by preventing the occurrence of burrs extending from the bead bottom surface inward in the tire radial direction with a simple configuration. The main object is to provide a manufacturing method and a molding apparatus.

  The invention according to claim 1 of the present invention is a method for manufacturing a pneumatic tire having a bead portion, and includes a step of forming a green cover and a vulcanization step of vulcanizing the green cover. The vulcanizing step includes a core having a bead lumen forming surface for forming at least the tire lumen surface of the bead portion, and the core is attached to the core from the outside in the tire axial direction and forms the bottom surface of the bead portion. And a bead ring having a bead bottom molding surface, and the core is bent inward in the tire axial direction from the inner edge in the tire radial direction of the bead lumen molding surface, thereby extending in the tire radial direction. A concave portion having an inward surface facing inward is provided, and the bead ring includes a protrusion that is connected to an inner side in the tire axial direction of the bead bottom molding surface and is inserted into the concave portion. .

  According to a second aspect of the present invention, in the pneumatic tire according to the first aspect, the inward surface extends at an angle of 0 to 15 degrees with respect to a tire axial direction from an inner edge in the tire radial direction of the bead lumen forming surface. It is a manufacturing method.

  According to a third aspect of the present invention, the bead bottom molding surface has a tire angled from the inner edge of the bead lumen molding surface in the tire radial direction at an angle of 5 to 20 degrees with respect to the tire axial direction and outward in the tire axial direction. It is a manufacturing method of the pneumatic tire of Claim 1 or 2 which inclines radially outward.

  The invention according to claim 4 includes a step of removing a cured product of excess rubber guided between the protrusion and the inward surface of the recess after the vulcanization step. This is a method of manufacturing a crab pneumatic tire.

  According to a fifth aspect of the present invention, the core includes a replaceable ring shape including a core body constituting a main portion of the core and a part of a bead lumen forming surface including the inward surface. It is a manufacturing method of the pneumatic tire in any one of Claims 1 thru | or 4 comprised including these attachment pieces.

  According to a sixth aspect of the present invention, there is provided a molding apparatus for vulcanizing a pneumatic tire having a bead portion, the core having a bead lumen molding surface for molding at least the tire lumen surface of the bead portion. And a bead ring having a bead bottom molding surface that is attached to the core from the outer side in the tire axial direction and that forms the bottom surface of the bead portion, the core in the tire radial direction of the bead lumen molding surface A concave portion having an inward surface facing inward in the tire radial direction by bending inward in the tire axial direction from the inner edge, and the bead ring is continuous with the inner side in the tire axial direction of the bead bottom molding surface and A pneumatic tire molding apparatus comprising a protrusion inserted into a recess.

  The invention according to claim 7 is the pneumatic tire according to claim 6, wherein the inward surface extends from an inner edge in the tire radial direction of the bead lumen forming surface at an angle of 0 to 15 degrees with respect to a tire axial direction. This is a molding apparatus.

  Further, in the invention according to claim 8, the bead bottom molding surface is a tire that is at an angle of 5 to 20 degrees with respect to the tire axial direction from an inner edge in the tire radial direction of the bead lumen molding surface and outward in the tire axial direction. The pneumatic tire molding apparatus according to claim 6 or 7, wherein the pneumatic tire is inclined outward in the radial direction.

  According to a ninth aspect of the present invention, the core includes a replaceable ring-shaped structure including a core body constituting a main portion of the core and a part of a bead lumen forming surface including the inwardly facing surface. The pneumatic tire molding apparatus according to any one of claims 6 to 8, wherein the pneumatic tire molding apparatus is configured to include the attachment piece.

  The method for manufacturing a pneumatic tire according to claim 1 and the molding apparatus according to claim 5 include a core having a bead lumen molding surface for molding at least a tire lumen surface of a bead portion, and an outer side in the tire axial direction on the core. The vulcanization process (vulcanization molding) is performed using a molding apparatus including a bead ring having a bead bottom molding surface that is mounted from above and that forms the bottom surface of the bead portion.

  The core includes a recess having an inward surface facing inward in the tire radial direction by bending inward in the tire axial direction from an inner edge in the tire radial direction of the bead lumen forming surface. The bead ring includes a protrusion that is continuous with the inside of the tire bottom direction of the bead bottom molding surface and is inserted into the recess. As a result, a part of the excess rubber in the bead portion is guided in a minute gap between the protrusion and the inward surface of the recess, and the occurrence of burrs extending inward in the tire radial direction from the bead bottom surface is prevented. Therefore, the pneumatic tire obtained by such a manufacturing method or molding apparatus has improved uniformity.

  Further, as in the invention according to claim 2 or 7, when the angle of the inward surface with respect to the tire axial direction is limited to a range of 0 to 15 degrees with respect to the tire axial direction, burrs made of surplus rubber are generally tires. It is formed in the range of 0 to 15 degrees with respect to the axial direction. Since such burrs do not become an obstacle at the time of rim assembly, even if they cannot be completely removed, deterioration of tire uniformity can be reliably prevented.

It is sectional drawing of the pneumatic tire obtained with the manufacturing method of this invention. It is sectional drawing of the vulcanization molding apparatus of this embodiment. It is an expanded sectional view explaining the recessed part of a core. It is sectional drawing explaining a bead ring. It is sectional drawing explaining the process of shape | molding a raw cover. It is sectional drawing explaining the vulcanization | cure process which vulcanizes a raw cover. It is an expanded sectional view of the bead part of the pneumatic tire which shows the effect of the present invention. It is sectional drawing which shows the manufacturing method of the pneumatic tire of other embodiment. (A) is sectional drawing which shows the manufacturing method of the conventional pneumatic tire, (b) is the A section enlarged view. It is sectional drawing of the bead part of the pneumatic tire obtained with the manufacturing method of the conventional pneumatic tire.

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 obtained with the manufacturing method 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 toroid shape, and end portions 6 e on both sides thereof are terminated in the bead core without being folded back by the bead core 5. An inner liner 20 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. Have. 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 30 for vulcanizing and molding the pneumatic tire 1. The molding apparatus 30 according to the present embodiment includes, for example, a split mold M and a hard core N disposed in the cavity of the split mold M. In FIG. 2, the split mold M is completely closed. Thereby, a molding space c for vulcanizing the pneumatic tire 1 is formed between the split 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 split 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.

  FIG. 3 shows a partially enlarged view near the bead lumen forming surface 9c. The core N includes a concave portion 17 having an inward surface 14 facing inward in the tire radial direction by bending inward from the inner edge 9ce in the tire radial direction of the bead lumen forming surface 9c in the tire radial direction.

  The recess 17 includes the inward surface 14, a bottom surface 15 extending inward in the tire radial direction from an inner end 14 i in the tire axial direction of the inward surface 14, and a tire from an inner end 15 i in the tire radial direction of the bottom surface 15. And an outwardly extending surface 16 extending in the axial direction.

  The inward surface 14 is formed as an inclined surface having an angle α1 that goes inward in the tire radial direction toward the inside in the tire axial direction. On the other hand, the bottom surface 15 and the outward surface 16 of the present embodiment are formed by planes along the tire radial direction and the tire axial direction, respectively, in the cross section. Thereby, the concave portion 17 of the present embodiment has a substantially tapered shape in which the height L1 in the tire radial direction gradually decreases from the outer side in the tire axial direction toward the inner side, and is continuously formed in the tire circumferential direction. Needless to say, the depth W1 and the like of the recess 17 can be determined as appropriate.

  Further, a longitudinal side surface 19 extending from the outer end 16e inward in the tire radial direction is formed at the outer end 16e of the recess 17 in the tire axial direction.

  As shown in FIG. 2, the split mold M molds the outer surface of the sidewall portion 3 and the tread ring M <b> 1 capable of expanding and contracting the diameter of the tread portion 2 of the raw cover 1 a (pneumatic tire), for example. A pair of side rings M2 that can move in the tire axial direction, and a pair of bead rings M3 that can form at least the bottom surface 4s of the bead portion 4 and can move in the tire axial direction.

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

  The bead ring M3 of the present embodiment has a ring shape (not shown) continuous in the tire circumferential direction, and the bead bottom for forming the bottom surface 4s (shown in FIG. 3) of the bead portion 4 as shown in FIG. A molding surface 10a and a bead outer surface molding surface 10c that is connected to the heel side of the bead bottom molding surface 10a via an arc surface 10b and that molds the outer surface 4o in the tire axial direction of the bead portion 4 (shown in FIG. 3). Have. The bead bottom molding surface 10a is formed as an inclined surface having an angle α2 that extends outward in the tire radial direction toward the outer side in the tire axial direction.

  The angle α2 of the bead bottom molding surface 10a is preferably 5 degrees or more, more preferably 10 degrees or more, and preferably 20 degrees or less, more preferably 18 degrees or less, according to the custom. If the angle α2 is less than 5 degrees, the ability to remove the bead ring M3 is lowered. Conversely, if the angle α2 exceeds 20 degrees, the rubber flow in the bead portion becomes large, and molding defects may easily occur.

  Further, the bead ring M3 is connected to the inner side of the bead bottom molding surface 10a in the tire axial direction, specifically, the inner end 10ae of the bead bottom molding surface 10a, and is inserted into the recess 17 (shown in FIG. 3) of the core. The projection 18 is provided.

  In the present embodiment, the protrusion 18 has an outer surface 18a facing outward in the tire radial direction, an end surface 18b extending to the outer surface 18a and extending inward in the tire radial direction, and an inner surface extending to the tire axial direction extending to the end surface 18b. 18c.

  The outer surface 18a of the protrusion 18 is connected to the inner end 10ae of the bead bottom molding surface 10a and has an inclination in the same direction as the bead bottom molding surface 10a, that is, an angle α3 directed inward in the tire radial direction toward the inner side in the tire axial direction. It is formed as an inclined surface. Further, the end surface 18b and the inner surface 18c of the protrusion 18 of the present embodiment extend substantially parallel to the tire radial direction and the tire axial direction, respectively. A longitudinal surface 21 extending inward along the tire radial direction is formed at the outer end 18ce of the inner surface 18c of the protrusion 18 in the tire axial direction.

  Further, as shown in FIGS. 3 and 4, such a protrusion 18 is inserted into the recess 17 provided in the core N by moving the bead ring M <b> 3 inward in the tire axial direction. Further, the bead ring M3 abuts on the vertical side surface 19 of the core N, whereby the position in the tire axial direction is uniquely determined. In the present embodiment, the angle α1 of the inward surface 14 of the recess 17 and the angle α3 of the outer surface 18a of the protrusion 18 are substantially the same, and the vertical surface 21 of the bead ring M3 is the core N. The outer diameter is designed so that both surfaces 14 and 18a overlap closely with each other when they are in contact with the vertical side surface 19. Thereby, when the split mold M is closed, the core N and the bead ring M3 are easily aligned. At this time, the end surface 18 b of the protrusion does not contact the bottom surface 15 of the recess 17.

  Further, as shown in FIG. 3, the inward surface 14 of the concave portion 17 is likely to be worn because it frequently contacts the protrusion 18 as the bead ring M3 moves in the tire axial direction (opening / closing operation). In order to efficiently perform maintenance of such wear, the core N includes a core body 12 constituting a main part of the core and a part of the bead lumen forming surface 9c including the inwardly facing surface 14. It is desirable to include a replaceable ring-shaped attachment piece 13 to be configured.

  The attachment piece 13 has a substantially rectangular cross section and is integrally fixed to the core body 12 with a bolt or the like from the inside of the core N (not shown). And by removing the said volt | bolt, the attachment piece 13 can be removed from the core main body 12 to a tire axial direction outer side. Such a core N is desirable in that it can efficiently maintain the inwardly facing surface 14 with severe wear by only replacing the attachment piece 13 without repairing the entire core.

  A method for manufacturing the pneumatic tire 1 using the molding apparatus 30 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. 5, 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 20, the base portion 4Ga inside the clinch rubber 4G in the tire axial direction, the bottom portion 4Gb of the clinch rubber 4G, the inner core piece 5i, the carcass ply 6A, the outer core piece 5o, the tire axial direction outside of the clinch rubber 4G. The base 4Gc side wall rubber 3G, belt plies 7A and 7B, and 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 process, the split mold M is opened, and the raw cover 1a is put together with the core N into the cavity c (shown in FIG. 2). Then, as shown in FIG. 6, the bead ring M3, the side ring M2, and the tread ring M1 are closed, and the split mold M and / or the core N are heated, whereby the raw cover 1a is vulcanized. Due to the volume of the raw cover 1a with respect to the molding space and the expansion of the rubber material, the pressure of the rubber plasticized in the molding space rises and tries to enter the seam of the split mold M with low resistance. In particular, surplus rubber in the bead portion 4 enters a minute gap between the projection 18 and the inward surface 14 of the recess 17, part of which is less resistant.

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

  As shown in FIG. 7, the bead portion 4 of the pneumatic tire 1 manufactured through such a process is formed on the toe side into a minute gap between the protrusion 18 and the inward surface 14 of the recess 17. A burr p2 that is a cured product of the surplus rubber that has entered is formed. However, such a burr p2 extends from the bottom surface 4s of the bead portion 4 to the inside in the tire axial direction, and is different from that extending inward in the tire radial direction as shown in FIG. Further, the burr p2 does not hinder the rim assembly, and the diameter of the bottom surface 4s of the bead portion 4 can be kept uniform. Therefore, the pneumatic tire 1 obtained by the manufacturing method or the molding apparatus of the present embodiment is excellent in uniformity.

  Note that, after the vulcanization step, the burr p2 is preferably cut by a trimming step or the like.

  In particular, as shown in FIG. 3, when the inward surface 14 extends from the inner edge 9ce of the bead lumen forming surface 9c in the tire radial direction at an angle α1 of 0 to 15 degrees with respect to the tire axial direction (to this) The angle α3 (shown in FIG. 4) of the outer surface 18a of the engaging protrusion 18 is also substantially the same as the angle α1, and the burr p2 is formed at an angle α4 along the same. Since such a burr p2 does not become an obstacle at the time of rim assembly, even if it cannot be completely removed, it is possible to reliably prevent deterioration of tire uniformity, and particularly to improve RFV (radial force variation). . From such a viewpoint and the viewpoint of suppressing the wear of the inward surface 14, the angle α1 of the inward surface 14 is preferably 8 degrees or more, and more preferably 12 degrees or less. In particular, it is preferable in that the burr p2 can be further away from the rim by making the angle α1 of the inward surface 14 smaller than the angle α2 of the bead bottom molding surface 10a.

FIG. 8 shows another method for manufacturing a pneumatic tire 1 and a molding apparatus 31 of the present invention.
The core N of the previous embodiment has the molding surface 9 that molds the entire area of the lumen surface i of the pneumatic tire 1. However, 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 vulcanized using a bladder b made of a crosslinked rubber. Other parts are the same as those in the above embodiment. Accordingly, even in such an embodiment, the surplus rubber in the bead portion 4 is guided between the protrusion 18 and the inward surface 14 of the recess 17, so that a pneumatic tire excellent in uniformity is manufactured.

  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.

In order to confirm the effect of the present invention, a pneumatic radial tire of size 215 / 45R17 was prototyped based on the specifications in Table 1 after molding a green cover using a core and a bead ring and vulcanizing. The angle α3 of the outer surface of the protrusion was the same as the angle α1 of the inward surface of the recess of the core, and the angle α2 of the bead bottom molding surface was 17 degrees. Each tire has the common internal structure shown in FIG.
The main common specifications are as follows.
<Carcass>
Number of carcass plies: 1 Carcass cord material: Polyester Carcass cord angle: 90 degrees <Belt layer>
Number of plies: 2 Belt cord: Steel Belt cord angle: + 22 ° / −22 ° The test method is as follows.

<Tire uniformity>
For each test tire, RFV was measured under the following conditions in accordance with the uniformity test conditions of JASO C607: 2000 (average value of 10 tests). The evaluation was performed using an index in which each RFV was reciprocal and Comparative Example 1 was set to 100. The larger the value, the better.
Rims: 8.0 x 17
Internal pressure: 200 kPa
Load: 4kN
Tire rotation speed: 60rpm

<Abrasion of attachment piece>
After 10 test tires were manufactured, the state of wear on the inward surface of the attachment piece was measured. In the evaluation, the average of the wear length at the inner edge in the tire radial direction of the bead lumen forming surface measured at four locations in the tire circumferential direction was reciprocalized, and the evaluation was performed using an index with the wear state of Example 1 as 100. The larger the value, the smaller the wear and the better.
The test results are shown in Table 1.

  As a result of the test, it was confirmed that the uniformity of the example was improved as compared with the comparative example.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 1a Raw cover 2 Tread part 3 Side wall part 4 Bead part 4s Bottom face of bead part 5 Bead core 6 Carcass ply 9c Bead inner cavity molding surface 9ce Inner edge 10a of bead inner cavity molding surface Bead bottom molding surface 14 Inwardly facing surface 17 of the recessed portion 18 Recessed portion 18 Protrusion i Tire bore surface M3 Bead ring N, N1 Core

Claims (9)

A method for manufacturing a pneumatic tire having a bead portion,
Forming a raw cover;
A vulcanization step of vulcanizing the green cover,
The vulcanization step includes a core having a bead lumen molding surface for molding at least a tire lumen surface of the bead portion, and a bead that is attached to the core from the outer side in the tire axial direction and molds the bottom surface of the bead portion. Is performed using a molding apparatus including a bead ring having a bottom molding surface,
The core includes a recess having an inward surface facing inward in the tire radial direction by bending inward in the tire axial direction from an inner edge in the tire radial direction of the bead lumen forming surface,
The method of manufacturing a pneumatic tire according to claim 1, wherein the bead ring includes a protrusion that is connected to an inner side of the bead bottom molding surface in the tire axial direction and is inserted into the recess.   2. The method for manufacturing a pneumatic tire according to claim 1, wherein the inward surface extends from an inner edge in a tire radial direction of the bead lumen forming surface at an angle of 0 to 15 degrees with respect to a tire axial direction.   The bead bottom molding surface is inclined outwardly in the tire radial direction from the inner edge in the tire radial direction of the bead lumen molding surface at an angle of 5 to 20 degrees with respect to the tire axial direction and outward in the tire axial direction. A method for producing a pneumatic tire according to 1 or 2.   The manufacturing of the pneumatic tire according to any one of claims 1 to 3, further comprising a step of removing a cured product of excess rubber guided between the protrusion and the inward surface of the concave portion after the vulcanizing step. Method.   The core includes a core body that constitutes a main part of the core, and a replaceable ring-shaped attachment piece that includes the inward surface and forms a part of a bead lumen forming surface. A method for manufacturing a pneumatic tire according to any one of claims 1 to 4. A molding apparatus for vulcanizing a pneumatic tire having a bead portion,
A core having a bead lumen molding surface for molding at least the tire lumen surface of the bead portion, and a bead having a bead bottom molding surface mounted on the core from the outside in the tire axial direction and molding the bottom surface of the bead portion. Including rings,
The core includes a recess having an inward surface facing inward in the tire radial direction by bending inward in the tire axial direction from an inner edge in the tire radial direction of the bead lumen forming surface,
2. The pneumatic tire molding apparatus according to claim 1, wherein the bead ring includes a projection that is connected to an inner side of the bead bottom molding surface in the tire axial direction and is inserted into the recess.   The pneumatic tire molding apparatus according to claim 6, wherein the inward surface extends from an inner edge in the tire radial direction of the bead lumen molding surface at an angle of 0 to 15 degrees with respect to a tire axial direction.   The bead bottom molding surface is inclined outwardly in the tire radial direction from the inner edge in the tire radial direction of the bead lumen molding surface at an angle of 5 to 20 degrees with respect to the tire axial direction and outward in the tire axial direction. The pneumatic tire molding apparatus according to 6 or 7.   The core includes a core body that constitutes a main part of the core, and a replaceable ring-shaped attachment piece that includes the inward surface and forms a part of a bead lumen forming surface. The pneumatic tire molding apparatus according to any one of claims 6 to 8.

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