JP6317642B2 - Pneumatic tire, method for manufacturing pneumatic tire, and molding drum used in the manufacturing method - Google Patents

Description

  The present invention relates to a pneumatic tire with improved high-speed durability performance, a method for manufacturing such a pneumatic tire, and a molding drum used in the manufacturing method.

  For example, a pneumatic tire is provided with a belt layer in which a plurality of belt plies each having a steel cord disposed outside the carcass tire radius and inside the tread portion are stacked in the tire radial direction. The belt ply has a cut surface of a steel cord at its side edge. For this reason, for example, at the contact position between the tread rubber of the tread portion and the cut surface of the steel cord, damage of the tread portion due to peeling of the steel cord (BEL: BREKEAR EDGE LOOSENS) occurs, and the high-speed durability performance deteriorates. there were.

  In order to solve the above-mentioned problems, for example, the cut surface of the steel cord is covered with an edge cover made of the same rubber material as the topping rubber constituting the belt layer in a substantially U shape in cross-section, and the tread rubber or the like and steel are covered. It is known to suppress contact with the cut surface of the cord.

  As a method of manufacturing such a belt ply, for example, it is known to attach an edge cover simultaneously with the molding of the ply material of the belt ply. That is, as shown in FIG. 8 (a), after forming the ply material a, the narrow and sheet-like edge cover b manufactured by a calender device (not shown) has side edges c and c on both sides of the ply material a. It was pasted on. Since the side edge c of the ply material a is covered with the edge cover b, the position of the side edge c is difficult to specify. For this reason, there existed a problem that the sticking precision of the ply material a deteriorated and production efficiency fell easily.

  Further, instead of such a belt ply manufacturing method, as shown in FIG. 8B, after the ply material a to which the edge cover b is not attached is placed on the molding drum e, the edge cover is covered. A manufacturing method in which b is wound around the side edge to form a belt layer g is known. However, this method has a problem in that the side edge of the ply material a cannot be folded back by the edge cover and the cut surface of the steel cord cannot be effectively covered, so that the effect of suppressing the generation of BEL is small. It was.

JP 2012-224034 A

  The present invention has been devised in view of the above circumstances, and is based on the improvement of a forming drum for forming a belt layer and a method for attaching an edge cover using the forming drum. Main object of the present invention is to provide a pneumatic tire capable of efficiently and effectively covering the side edges of the tire and improving the high-speed durability performance, a method for manufacturing the pneumatic tire, and a molding drum used in the manufacturing method. It is said.

  The present invention relates to an annular ply laminate in which a plurality of belt plies are stacked using a forming drum, an edge cover that is folded back in a U shape and covers an outer end portion in the drum axial direction of the ply laminate. A pneumatic tire manufacturing method including a belt forming step of forming a belt layer having a central drum, wherein the molding drum is disposed on both sides of the central drum in the axial direction of the drum and the central drum is caused by inflow of high-pressure air. A side drum having a bladder that can expand radially outward beyond the outer peripheral surface of the drum, and the bladder has an annular restricted region in which expansion outward in the radial direction is restricted to a restricted range, and the restricted region And the belt forming step is formed between the central drum and the central drum. An edge cover winding step for winding the edge cover around the outer peripheral surface of the central drum, and a ply for sequentially winding a plurality of belt plies on the edge cover. A winding step having a winding step, and a folding step of folding the protruding portion into the U shape inward in the axial direction due to expansion of the bladder, and the folding step includes the restricted region and the non-restricted region. By both expanding to the restriction range, the first step of raising the protruding portion radially outward, only the non-restricted area expands beyond the restriction range, and a part of the non-restricted area By bulging inward in the drum axial direction beyond the outer end of the central drum, the raised protrusion is moved inward in the axial direction. Characterized in that it comprises a second step of kicking affixed to the radially outermost belt ply return Ri.

  In the method for manufacturing a pneumatic tire according to the present invention, the restriction region is formed by winding a low-stretch belt in the circumferential direction on the outer peripheral surface of the bladder and in the center in the width direction. desirable.

  The present invention is a pneumatic tire formed by the manufacturing method according to claim 1 or 2.

  The present invention is a molding drum used in the manufacturing method according to claim 1 or 2, wherein the central drum is disposed on both sides of the central drum in the drum axial direction, and the outer peripheral surface of the central drum is formed by inflow of high-pressure air. And a side drum having a bladder that can expand radially outwardly, and the bladder includes an annular restriction region in which expansion outward in the radial direction is restricted to a restricted range, and the restriction region and the central drum. It is divided into a non-restricted region that is located in between and can expand radially outward beyond the restriction range.

  The method for producing a pneumatic tire according to the present invention includes a belt forming step of forming a belt layer in which the outer end portion of the ply laminated body in which the belt plies are stacked is collectively covered with an edge cover using a forming drum. ing. The forming drum includes a side drum having a central drum around which an edge cover and a ply laminate are wound outward from the outer end in the drum axial direction, and a bladder that can expand radially outward beyond the outer peripheral surface of the central drum. It has. The bladder is divided into an annular restriction region in which expansion outward in the radial direction is restricted to a restricted range, and a non-restricted region that can expand radially outward beyond the restriction range.

  The belt forming process includes a folding process. In the folding process, both the restricted area and the non-restricted area of the bladder expand to the restricted range, so that the protruding portion of the edge cover rises radially outward, and only the unrestricted area exceeds the restricted range. While expanding, a part of the unrestricted area bulges inward in the axial direction of the drum beyond the outer edge of the central drum, so that the protruding part is folded back in the U-shape in the axial direction and attached to the outermost belt ply in the radial direction And a second step. Thereby, the innermost and outermost sides in the drum radial direction of the ply laminate and the outer side in the drum axial direction can be covered with the edge cover. For this reason, contact between the belt cord and another rubber material is suppressed, and generation of BEL is suppressed, so that high-speed durability performance is improved. Further, the edge cover can be easily folded by a forming drum having a simple structure including such a central drum and a side drum having a bladder.

  Furthermore, since the position of the side edge of the belt ply can be easily confirmed and wound around the central drum, the belt ply attaching accuracy is ensured to be high. Moreover, since the edge cover is collectively wound around the ply laminate, the production efficiency is improved.

It is sectional drawing of the pneumatic tire which shows one Embodiment of this invention. It is a side view which shows one Embodiment of the tire formation line used for the manufacturing method of the pneumatic tire of this invention. It is a perspective view of a belt layer forming device. It is sectional drawing of the forming drum explaining a winding process. (A) And (b) is a fragmentary sectional view of the forming drum explaining a folding process. (A) And (b) is sectional drawing of the belt layer manufactured with the manufacturing method of the tire of one Example of this invention. (A)-(c) is sectional drawing of the belt layer manufactured with the manufacturing method of the tire of a comparative example. (A) is a perspective view explaining the conventional belt ply, (b) is sectional drawing explaining the problem by the manufacturing method of the other conventional belt layer.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view of an embodiment of a pneumatic tire 1 manufactured by the method for manufacturing a pneumatic tire of the present invention. As shown in FIG. 1, a pneumatic tire (hereinafter sometimes simply referred to as “tire”) 1 of the present embodiment is suitably used as, for example, a tire for passenger cars or a heavy load tire for trucks and buses. Can be used.

  The 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. Yes.

  The carcass 6 is constituted by, for example, one carcass ply 6A. The carcass ply 6 </ b> A includes a main body portion 6 a that extends from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4, and a folded portion 6 b that is connected to the main body portion 6 a and is folded around the bead core 5. .

  The carcass ply 6A has a carcass cord arranged with an inclination of, for example, 75 to 90 degrees with respect to the tire equator C. For this carcass cord, for example, an organic fiber cord such as nylon, polyester, or rayon is suitably employed. A bead apex rubber Ba made of hard rubber is provided between the main body 6a and the folded portion 6b.

  The belt layer 7 includes an annular ply laminate 7A on which a plurality of belt plies 8 are overlaid, and an edge cover 7B that covers an outer end portion 7s of the ply laminate 7A in the drum axial direction.

  In the present embodiment, the ply laminate 7A is composed of two belt plies 8a and 8b inside and outside in the tire radial direction. Each belt ply 8a, 8b has a plurality of highly elastic belt cords (not shown) such as steel cords that are inclined at an angle of 15 to 40 ° with respect to the tire equator C.

  In this embodiment, the edge cover 7B covers the outer end portions 7s and 7s on both sides of the ply laminate 7A. The edge cover 7B includes an inner portion 9a in contact with the inner surface in the tire radial direction of the inner belt ply 8a, an outer portion 9b in contact with the outer surface in the tire radial direction of the outer belt ply 8b, and the outer end 7e of the ply laminate 7A. Is formed by being folded back into a U-shape including a joint portion 9c that connects the inner portion 9a and the outer portion 9b.

  In the present embodiment, a band layer 10 in which a band cord such as a nylon cord is spirally wound is provided on the outer side in the tire radial direction of the belt layer 7. The band layer 10 is formed of, for example, a full band ply 10A having the same axial width as the belt layer 7 and a pair of edge band plies 10B and 10B arranged only on the outer side in the tire axial direction of the belt layer 7. Has been.

  The tire 1 further includes a sidewall rubber 3G disposed on the outer side in the tire axial direction of the carcass 6 in the sidewall portion 3, and a tread rubber 2G that forms a ground contact surface 2a in the tread portion 2.

  FIG. 2 is a side view conceptually showing a tire forming line 11 for forming such a tire 1. As shown in FIG. 2, the tire forming line 11 includes, for example, a tire case forming device 12 that forms a cylindrical tire case Ta, a belt layer forming device 13 that forms a belt layer 7, and a tread ring that includes the belt layer 7. A tread ring conveying device 14 that conveys Tb and a raw tire forming device 15 that forms the raw tire 1A before vulcanization by pressing and attaching the tread ring Tb to the tire case Ta are included.

  The tire case molding device 12 of this embodiment has a known structure. The tire case molding device 12 includes, for example, a band drum 16 having an outer peripheral surface 16a around which tire constituent members such as a sheet-like carcass ply 6A and sidewall rubber 3G are wound, and a tire case Ta formed on the band drum 16. Tire case transporting means 17 for transporting the tire to the raw tire forming device 15. As the tire constituent member, a bead core 5, a bead apex rubber Ba, an inner liner, a bead reinforcement layer, and the like can be appropriately included depending on the tire structure. The bead core 5 and the bead apex rubber Ba may be extrapolated to the carcass ply 6A by the raw tire forming device 15, for example.

  In the present embodiment, the tread ring conveying device 14 has a known structure. The tread ring conveying device 14 has an adsorbing means 14a that adsorbs and holds the tread ring Tb, and conveys the tread ring Tb from the belt layer forming device 13 to a standby position P1 radially outside the raw tire forming device 15.

  In this embodiment, the raw tire forming apparatus 15 includes a shaping former 18 having a known structure that inflates the tire case Ta conveyed by the tire case conveying means 17 from a cylindrical shape to a toroidal shape. The shaping former 18 includes, for example, a drum portion 18A and a pair of bead receiving portions 18B that can move in and out of the tire axial direction and hold the bead portion of the tire case Ta. The shaping former 18 further has an inflatable rubber bladder (not shown) extending between the bead receiving portions 18B, 18B. A raw tire 1A is formed by pressing the inner peripheral surface of the tread ring Tb against the bulging portion of the tire case Ta inflated by the shaping former 18.

  The belt layer forming apparatus 13 includes a forming drum 20 including a central drum 21 and a pair of side drums 22 and 22 disposed on both sides of the central drum 21 in the drum axial direction, and a support capable of rotating and holding the forming drum 20. A shaft 23 is included.

  FIG. 3 is a perspective view of the belt layer forming apparatus 13. As shown in FIG. 3, the central drum 21 has a cylindrical shape with both axial sides open, and is divided into, for example, a tire circumferential direction and a plurality of metal materials forming an annular shape by abutting the divided surfaces. It has a segment 24 consisting of The segment 24 is supported so as to be movable inward and outward in the radial direction by, for example, an expansion / contraction diameter means (not shown) which is a well-known cylinder attached to the support shaft 23.

  The support shaft 23 supports the pair of side drums 22 and 22 and the central drum 21 concentrically. For example, an electric motor (not shown) that rotates the support shaft 23 is provided on one end side, and a drum portion 18A (shown in FIG. 2) of the raw tire forming device 15 is connected to the other end side. That is, in this embodiment, the forming drum 20 of the belt layer forming apparatus 13 and the drum portion 18A of the shaping former 18 are held concentrically and rotatably.

  The side drum 22 has an inlet (not shown) through which high-pressure air flows, and has a bladder 25 that can expand outward in the drum radial direction when high-pressure air flows in.

  In the initial state before the belt ply 8 is wound, the side drum 22 is formed so that the outer diameter of the drum including the bladder 25 is smaller than that of the central drum 21.

  The bladder 25 of the present embodiment is made of a rubber material and has a cylindrical shape. On both sides of the bladder 25 in the drum axis direction, flanges 26 and 26 made of, for example, a metal material are provided. The flange 26 restrains the movement and expansion of the bladder 25 to both sides in the drum axial direction, and induces expansion in the drum radial direction.

  The bladder 25 is divided into an annular restricted region 27 in which expansion outward in the radial direction is restricted to a restricted range, and a non-restricted region 28 that can expand radially outward beyond the restricted range. The restriction range is set at a radial position exceeding at least the outermost end 8t (shown in FIG. 4) in the tire radial direction of the ply laminate 7A.

  The restriction region 27 is formed by winding a belt 29 having extensibility lower than that of the bladder 25 on the outer peripheral surface 25a of the bladder 25 in the circumferential direction.

  The band 29 has a rigidity higher than that of the bladder 25. The band 29 is made of, for example, a rubber material having a higher tensile strength than the bladder 25. As a result, the expansion of the bladder 25 is limited by the band 29 in the portion where the band 29 is wound, and is governed by the expansion of the band 29. The belt 29 may be, for example, an annular cord ply covered with rubber by intersecting cords made of a plurality of organic fibers at an angle of 10 to 40 degrees with respect to the tire circumferential direction. The band body 29 of the present embodiment is fixed to the outer peripheral surface 25a of the bladder 25 with, for example, an adhesive.

  In the present embodiment, the non-restricted region 28 is a region where the outer peripheral surface 25a of the bladder 25 is exposed. The non-restricted region 28 includes a first portion 30 between the restricted region 27 and the central drum 21 and a second portion 31 outside the restricted region 27 in the drum axis direction. For this reason, when high-pressure air is introduced into the bladder 25, the bladder 25 on both sides of the belt body 29 expands outward in the drum radial direction, so that the belt body 29 expands substantially parallel to the drum axis. be able to. Thereby, a protruding portion 42 of the edge cover 7B described later is raised to the outside in the drum radial direction with high accuracy.

  As shown in FIG. 4, the bladder 25 further has an annular covering region 32 in which the outer peripheral surface 25 a is covered with the central drum 21 on the inner side in the drum axis direction of the first portion 30. The covering region 32 is a region in which expansion toward the outside in the radial direction is restricted by the central drum 21. The width W in the drum axis direction of the coating region 32 is preferably 0 mm or more, more preferably 5 mm or more, preferably 50 mm or less, more preferably 45 mm or less.

  In the present embodiment, the first portion 30 has a larger width in the drum shaft direction than the second portion 31. Thereby, the 1st part 30 can expand | swell largely radially outward by inflow of high pressure air.

Next, a method for manufacturing the tire 1 using such a tire forming line 11 will be described. The manufacturing method of the tire 1 of this embodiment is as follows:
(A) A tire case transfer step S1 for transferring the cylindrical tire case Ta formed on the band drum 16 to the raw tire forming device 15 by the tire case transporting means 17, and
(A) a belt forming step S2 for forming the belt layer 7 using the forming drum 20;
(C) A tread ring forming step S3 in which a tread component is wound around the outer side of the belt layer 7 in the tire radial direction to form a tread ring Tb;
(D) A tire forming step S4 in which the tire case Ta is expanded in a toroidal shape by the shaping former 18 and the tread ring Tb conveyed by the tread ring conveying device 14 is attached to the tire case Ta to form the raw tire 1A. Contains.

  Other than the belt forming step S2 and the tread ring forming step S3, the tire case transfer step S1, the raw tire forming step S4, and other manufacturing steps such as a vulcanizing step for vulcanizing the raw tire 1A, for example. Is the same as in the prior art.

  4 and 5 are partial side views for explaining the belt forming step S2. The belt forming step S2 includes a winding step T1 (FIG. 4) for winding the edge cover 7B and the belt ply 8 on the outer peripheral surface 21a of the central drum 21, and the edge cover 7B protruding from the outer end 21e of the central drum 21. This includes a folding step T2 (FIGS. 5A and 5B) for folding the protruding portion 42.

  As shown in FIG. 4, the winding step T1 includes an edge cover winding step for winding the edge cover 7B, and a ply winding step for sequentially winding a plurality of belt plies 8 on the edge cover 7B. Yes.

  In the edge cover winding step, the sheet-like edge cover 7B is wound around the outer periphery 21e of the central drum 21 so as to protrude outward in the drum axial direction. That is, the edge cover 7 </ b> B is divided into a base portion 41 disposed on the central drum 21 and a protruding portion 42 that protrudes from the central drum 21 and is disposed on the side drum 22. In the present embodiment, the outer end 9e in the axial direction of the edge cover 7B is located on the restriction region 27. In the edge cover winding step, the edge cover 7 </ b> B is wound on both sides of the central drum 21.

  The axial length L1 of the protruding portion 42 is preferably about 20 to 50 mm, for example. Further, the edge cover 7B preferably has an axial length L of, for example, about 50 to 100 mm, and a thickness D of, for example, 0.3 to 0.8 mm.

  In the ply winding step, in this embodiment, two belt plies 8a and 8b are wound. The belt ply 8 is formed of a cord ply 44 having a wide and rectangular cross section in which a plurality of belt cords (not shown) covered with a topping rubber are arranged in parallel. The cut surface of the belt cord is exposed at the side edge 44s of the cord ply 44.

  The belt ply 8a in the present embodiment has both ends 8e, 8e positioned at the inner side in the drum axial direction than the outer end 21e of the central drum 21 and the inner end 9i of the edge cover 7B in the drum axial direction. It is arranged outside in the drum axis direction. Thus, in the present embodiment, the inner belt ply 8a does not have a protruding portion that protrudes outward from the outer end 21e of the central drum 21 in the drum axial direction. The inner surface of the inner belt ply 8a in the drum radial direction is in contact with the edge cover 7B. The inner belt ply 8a may have a form (not shown) in which both ends 8e, 8e are arranged on the outer side in the drum axial direction than the outer end 21e of the central drum 21.

  In the present embodiment, the outer belt ply 8b is provided at positions where both ends 8i, 8i are slightly inward in the drum axial direction from the outer end 8e of the inner belt ply 8a. That is, the outer belt ply 8b has a smaller axial length than the inner belt ply 8a. It should be noted that the outer belt ply 8b is not limited to such an aspect, and may be, for example, an aspect wider than the inner belt ply 8a.

  Next, a folding step T2 is performed. As shown in FIGS. 5A and 5B, the folding step T2 of the present embodiment includes a first step of raising the protruding portion 42 of the edge cover 7B to the outside in the drum radial direction, and the raised protruding portion. A second step of folding the belt 42 inward in the drum axial direction and sticking it to the outer belt ply 8b.

  As shown in FIG. 5A, in the first step, high-pressure air is introduced from an air supply port (not shown) of the bladder 25, and both the restricted region 27 and the non-restricted region 28 are expanded to the restricted range. . At this time, the length of the bladder 25 in the drum radial direction is expanded to about 1.2 to 1.5 times that in the winding step T1, for example. Thereby, the pressing force of the bladder 25 acts on the protruding portion 42, and the protruding portion 42 is raised outward in the radial direction. In the present embodiment, since the covering region 32 is provided, the first portion 30 connected to the covering region 32 has the outer surface 42a of the protruding portion 42 on the inner side in the drum axial direction with the outer end 21e of the central drum 21 as a fulcrum. Launched to face. At this time, since the outer end 9e of the edge cover 7B is disposed on the outer side in the drum radial direction of the band 29, the expansion force of the first portion 30 effectively acts on the protruding portion 42. The belt 29 is moved inward in the drum axial direction by being pulled by the rising of the first portion 30 (extending outward in the drum radial direction).

  Next, as shown in FIG. 5B, in the second step, the high-pressure air further flows into the bladder 25. Thereby, when the expansion of the restriction area 27 is suppressed in the restriction range, only the non-restriction area 28 expands beyond the restriction range, so that in a part of the restriction area 28, in this embodiment, The outer portion 30a in the drum radial direction, which is a part of the first portion 30, swells inward in the drum axial direction beyond the outer end 21e of the central drum 21. As a result, the protruding portion 42 is pressed by the outer portion 30a, folded back in a U shape inward in the drum axial direction, and attached to the outer surface 8s of the outer ply 8b. Further, due to the expansion of the outer portion 30a toward the inside in the drum axial direction, the belt body 29 moves until it comes into contact with the outer end 21e of the central drum 21. As a result, the outer portion 30a is further pressed inward in the drum axial direction by the band 29 having rigidity larger than that of the bladder 25, so that the protruding portion 42 can be attached to the outer surface 8s of the outer ply 8b with high accuracy. it can.

  In the belt ply 8 formed by the folding process T2, the belt cord cut surfaces of the outer ends 8e and 8i of the belt ply 8 are effectively covered with the edge cover 7B. Is effectively suppressed, and as a result, high-speed durability performance is improved. In the present embodiment, after the ply laminate 7A is disposed on the outer peripheral surface of the forming drum 20, the edge cover 7B is folded back. Thereby, for example, a gap generated between the belt plies 8a and 8b adjacent to each other in the tire radial direction is suppressed, and the vulcanization failure in the vulcanization process is reduced, so that the high-speed durability performance is further improved.

  Next, a tread ring forming step S3 is performed. In the tread ring forming step S3, high-pressure air is discharged from the side drum 22 of the forming drum 20, and the initial state of the belt forming step S2 is obtained. Next, a tread constituent member including the band layer 9 and the tread rubber 2G is wound around the outer side of the belt layer 7 to form a tread ring Tb (not shown).

  Next, the tread ring Tb is adsorbed and held by the adsorbing means 14 a of the tread ring conveyance device 14. Next, the tread ring Tb is separated from the forming drum 20 and can be conveyed to the raw tire forming device 15 by contracting the segment 24 of the central drum 21 by means of an expansion / contraction diameter means (not shown) provided on the support shaft 23. It becomes a state. Next, the tread ring transport device 14 transports the tread ring Tb to the raw tire forming device 15.

  As mentioned above, although embodiment of this invention was explained in full detail, it cannot be overemphasized that this invention is not limited to illustrated embodiment, and can be deform | transformed and implemented in a various aspect.

A pneumatic tire of size 330 / 710R18 having the basic structure of FIG. 1 was prototyped based on the specifications in Table 1, and the high-speed durability performance of each sample tire was tested. The main common specifications and test methods for each sample tire are as follows. The same rubber material is used for the edge cover and the belt ply.
The test method is as follows.

<High-speed durability performance>
Using a drum tester with a diameter of 1.7 m, under the following conditions, the time until damage (abnormal noise) occurs in the tread of the sample tire and the vicinity of the tread edge of the sample tire when the damage occurs The surface temperature of was measured. The results are displayed as measured values. The damage occurrence time is better as the numerical value is larger. The lower the numerical value, the better the surface temperature.
Rims: 18 × 13JJ
Internal pressure: 3.0MPa
Load: 5.0kN
Speed: 250km / h
Edge cover axial length and thickness: same

  As a result of the test, it was confirmed that the tire of the example had improved high-speed durability performance compared to the comparative example. In addition, the test was performed by changing the tire size, and showed the same tendency as the test result.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 7 Belt layer 7A Ply laminated body 7B Edge cover 20 Molding drum 21 Central drum 22 Side drum 25 Bladder 27 Restriction area 28 Non-restriction area 42 A protrusion part

Claims (3)

A belt layer having an annular ply laminate in which a plurality of belt plies are stacked using a forming drum, and an edge cover that is folded back in a U shape and covers an outer end portion in the drum axial direction of the ply laminate. A pneumatic tire manufacturing method having a belt forming step of forming
The molding drum is
A central drum, and a side drum having a bladder disposed on both sides of the central drum in the axial direction of the central drum and capable of expanding radially outward beyond the outer peripheral surface of the central drum by inflow of high-pressure air;
In addition, the bladder may be positioned between the restriction region and the central drum and expand radially outward beyond the restriction range, and the annular restriction region where expansion outward in the radial direction is restricted to the restriction range. Is partitioned into unrestricted areas,
The belt forming step includes
An edge cover winding step of winding an edge cover on the outer peripheral surface of the central drum and having a protruding portion protruding outward from the outer end of the central drum in the drum axial direction;
A winding step having a ply winding step of sequentially winding a plurality of belt plies on the edge cover;
And a folding step of folding the protruding portion in the U shape in the axial direction inside due to the expansion of the bladder,
In addition, the folding step includes a first step of raising the protruding portion radially outward by expanding both the restriction region and the non-restriction region to the restriction range;
Only the non-restricted region expands beyond the restriction range, and a part of the non-restricted region swells inward in the drum axial direction beyond the outer end of the central drum. A pneumatic tire manufacturing method comprising: a second step of folding back inward in the axial direction and sticking to the outermost belt ply in the radial direction.   2. The pneumatic tire according to claim 1, wherein the restriction region is formed by winding a low-stretch belt in the circumferential direction on the outer peripheral surface of the bladder and in the center in the width direction. Production method. It is a forming drum used for the manufacturing method according to claim 1 or 2.
  A central drum, and a side drum having a bladder disposed on both sides of the central drum in the axial direction of the central drum and capable of expanding radially outward beyond the outer peripheral surface of the central drum by inflow of high-pressure air;
  In addition, the bladder may be positioned between the restriction region and the central drum and expand radially outward beyond the restriction range, and the annular restriction region where expansion outward in the radial direction is restricted to the restriction range. A forming drum characterized in that it is partitioned into an unrestricted region.

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