Tire molding mold and tire manufacturing method

Abstract

To provide a tire molding die that can reduce the driving force necessary for driving a segment at an initial stage of tire release, and a tire production method.SOLUTION: The present invention provides: a tire molding die 1 which is equipped with an annular tread molding part 20 configured to open and close when a plurality of segments 21 move in the radial direction, wherein each segment 21 has a design-surface split-die part 23 that is equipped with a tread design surface 20a for molding a tread 2c of a tire 2 and turns about a turning shaft 25 perpendicular to each of the movement direction of the segment 21 and the axial line of the tread molding part 20 when the tread molding part 20 is opened after the tire 2 undergoes vulcanization molding; and a tire production method using the die.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present invention relates to a tire molding mold and a tire manufacturing method. [Background technology]

[0002] Conventionally, as a tire molding mold used when manufacturing a tire by vulcanizing and molding an unvulcanized raw tire, there has been known a tire molding mold in which a circular tread molding portion (tread mold) that molds the tire tread is divided into a plurality of segments arranged in the circumferential direction, and each segment is configured to open and close by moving in the radial direction (for example, see Patent Documents 1 to 3). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2000-326332 A [Patent Document 2] JP 2000-334740 A [Patent Document 3] JP 2009-149079 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the above-mentioned conventional tire molding molds and tire manufacturing methods, when the tire is released from the tread molding section after vulcanization molding, each segment moves radially outward while maintaining its orientation relative to the tire tread. This causes the entire tread design surface that forms the tread of the segment to simultaneously peel off from the tread, resulting in a problem in that a large driving force is required to drive the segments in the initial stage of tire release.

[0005] The present invention has been made in consideration of the above-mentioned problems, and an object of the present invention is to provide a tire molding mold and a tire manufacturing method that can reduce the driving force required to drive the segments in the early stage of tire demolding. [Means for solving the problem]

[0006] The tire molding die of the present invention is a tire molding die that includes an annular tread molding section that is divided into a plurality of segments arranged in the circumferential direction and that is configured to open and close by radial movement of each of the segments, and that vulcanizes and molds an unvulcanized raw tire into a tire, wherein each of the segments has a tread design surface that molds the tread of the tire, and has a design surface divided mold section that is configured to rotate about a rotation axis that is perpendicular to each of the movement direction of the segments and the axis of the tread molding section when the tread molding section is opened after the tire has been vulcanized and molded, and each of the segments moves radially outward when the tread molding section is opened. , to accommodate a tire or a holder The present invention relates to a tire that is provided with a container and a holder that is driven radially outward by the container when the tread molding section is opened, the design surface division mold section being fixed to the radially inner side of the holder, and the holder being rotatably supported by the container by the rotation shaft. Each of the design surface division mold parts is attached between the corresponding holder and the container, and holds the corresponding design surface division mold part at a specified position by biasing the holder in a direction to attract the container, and has a spring member that elastically deforms to allow the holder to rotate relative to the container when the tread molding part is opened. , characterized in that

[0008] In one embodiment, the tire molding mold of the present invention can be configured so that the pivot axis is positioned radially outward from the radial center position of the holder and biased to one side in the axial direction from the center position of the axial direction of the tread molding portion of the holder.

[0009] As one embodiment, the tire molding mold of the present invention can be configured to have a spring member that is mounted between the corresponding holder and container, holds the corresponding design surface divided mold section in a specified position, and elastically deforms to allow the holder to rotate relative to the container when the tread molding section is opened.

[0010] The tire manufacturing method of the present invention is a tire manufacturing method for manufacturing a tire by vulcanizing and molding an unvulcanized raw tire using a tire molding die having an annular tread molding portion that is divided into a plurality of segments arranged in the circumferential direction and that is configured to open and close by moving each of the segments in a radial direction, and when each of the segments is moved radially outward to open the tread molding portion, the tire is released from the tread molding portion while rotating a design surface dividing mold portion provided on the segment about a rotation axis that is perpendicular to each of the moving direction of the segment and the axis of the tread molding portion, and each of the segments of the tire molding die is moved radially outward when the tread molding portion is opened. , to accommodate a tire or a holder The present invention is provided with a container and a holder that is driven radially outward by the container when the tread molding section is opened, the design surface division mold section is fixed to the radially inner side of the holder, and the holder is rotatably supported by the container by the rotation shaft. The spring members are respectively attached between the corresponding holders and the containers, and bias the holders in a direction to attract the containers, thereby holding the corresponding design surface division mold parts at specified positions, and elastically deform so as to allow the holders to rotate relative to the containers when the tread molding section is opened. The present invention is characterized by the use of Effect of the Invention

[0011] According to the present invention, it is possible to provide a tire molding die and a tire manufacturing method that are capable of reducing the driving force required to drive the segments in the initial stage of tire demolding. [Brief description of the drawings]

[0012] [Figure 1] 1 is a cross-sectional front view of a tire molding mold according to one embodiment of the present invention; [Diagram 2] 2 is a cross-sectional view of the tread molding portion shown in FIG. 1 in a plan view. [Diagram 3] FIG. 2 is a cross-sectional front view of the tire molding mold shown in FIG. 1 in an open state. [Figure 4] 2 is a cross-sectional view of the tread molding portion shown in FIG. 1 in an open state as viewed from above. [Diagram 5]FIG. 2 is an enlarged cross-sectional view of a main part of the tire molding die shown in FIG. 1 in detail. [Figure 6] FIG. 6 is a cross-sectional view in plan of one segment and an intermediate container shown in FIG. 5. [Figure 7] 6 is a cross-sectional view showing the details of the spring member shown in FIG. 5. [Figure 8] 6 is a cross-sectional view in plan view of one segment shown in FIG. 5, showing a state when the tire is released from the mold. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] A tire molding die and a tire manufacturing method according to an embodiment of the present invention will now be described in detail with reference to the drawings, in which the same reference numerals are used to designate common members and parts in the various drawings.

[0014] A tire molding mold 1 according to one embodiment of the present invention shown in FIG. 1 is used for manufacturing a tire 2 by molding a raw tire made mainly of unvulcanized (before vulcanization) synthetic rubber into a predetermined shape while vulcanizing it.

[0015] The tire 2 is a hollow tire made mainly of synthetic rubber, having a pair of sidewalls 2a, 2b and a tread 2c, and formed into a shape with a space therein that is filled with a gas such as air or nitrogen.

[0016] The tire molding die 1 includes a sidewall molding portion 10 and a tread molding portion 20 .

[0017] The sidewall molding portion 10 can be configured, for example, to include a circular lower sidewall molding portion 11 fixed to the upper surface of the lower container 3, and a circular upper sidewall molding portion 12 fixed to the lower surface of the upper container 4.

[0018] The sidewall molding section 10 can place (store) an annular tire 2 or raw tire between the lower sidewall molding section 11 and the upper sidewall molding section 12 in a position in which the central axis of the tire 2 or raw tire is coaxial with the central axis O of the sidewall molding section 10. The lower sidewall molding section 11 has an annular, upwardly facing lower sidewall design surface 11a centered on the central axis O, and the lower sidewall design surface 11a can mold the outer surface of one sidewall 2a of the tire 2 or raw tire (the side facing downward in FIG. 1). Similarly, the upper sidewall molding section 12 has an annular, downwardly facing upper sidewall design surface 12a centered on the central axis O, and the upper sidewall design surface 12a can mold the outer surface of the other sidewall 2b of the tire 2 or raw tire (the side facing upward in FIG. 1). 3, the upper container 4 moves upward relative to the lower container 3 (in a direction in which the two move away from each other along the central axis of the tire 2), thereby opening the sidewall molding section 10 and releasing the tire 2 from the sidewall molding section 10. Meanwhile, the upper container 4 moves downward to its original position shown in Fig. 1, thereby closing the sidewall molding section 10 from an open state to a state in which the tire 2 or green tire can be molded.

[0019] The configuration of the sidewall molding portion 10 can be appropriately changed, for example, so that the lower container 3 moves downward relative to the upper container 4 to open the sidewall molding portion 10.

[0020] The tread molding portion 20 has an annular shape coaxial with the sidewall molding portion 10, and is disposed adjacent to the radially outer sides of the lower sidewall molding portion 11 and the upper sidewall molding portion 12. An inner peripheral surface of the tread molding portion 20 facing radially inward forms a tread design surface 20a that molds the outer peripheral surface of the tread 2c of the tire 2.

[0021] As shown in Fig. 2, the tread molding portion 20 is divided into a plurality of segments 21 arranged in the circumferential direction. Each of the segments 21 has an arc shape in a plan view, and is combined in the circumferential direction to constitute the tread molding portion 20 as a ring-shaped mold as a whole. In this embodiment, the tread molding portion 20 is divided into nine segments 21 having the same circumferential length. The number of divisions of the tread molding portion 20 in the circumferential direction is preferably 7 to 13, but is not limited to this and can be changed as appropriate.

[0022] 1, each segment 21 has an outer circumferential surface facing radially outward fixed to the inside of the corresponding intermediate container 5, and is driven by the intermediate container 5 to move in a radial direction centered on the axis (central axis O) of the tread molding portion 20. The tread molding portion 20 can be opened and closed by the radial movement of each segment 21.

[0023] More specifically, the intermediate container 5 has, on its outer circumferential surface facing radially outward, a tapered surface 5a that is inclined so that the outer diameter gradually decreases toward the top. Meanwhile, an annular outer ring 6 arranged radially outward of the intermediate container 5 is fixed to the lower surface of the upper container 4. The outer ring 6 has, on its inner circumferential surface facing radially inward, a tapered surface 6a that is inclined so that the outer diameter gradually decreases toward the top. The outer ring 6 is connected to each intermediate container 5 by a guide member (not shown) or the like so that the tapered surface 6a slides vertically along the tapered surface 5a of the intermediate container 5.

[0024] When the upper container 4 moves upward relative to the lower container 3, the outer ring 6 moves upward relative to each intermediate container 5 while sliding the tapered surface 6a along the tapered surface 5a of the intermediate container 5, and as a result, as shown in FIG. 3, each intermediate container 5 moves radially outward around the axis of the tread molding section 20. When each intermediate container 5 moves radially outward around the axis of the tread molding section 20, as shown in FIG. 3 and FIG. 4, each segment 21 is driven by the corresponding intermediate container 5 and moves radially outward together with the intermediate container 5. As a result, the tread molding section 20 is opened to a position where the tread design surface 20a is separated from the tire 2 or the tread 2c of the raw tire. Note that the tread molding section 20 may be configured to rise to a position (a position above the position shown in FIG. 3) where the molded tire 2 can be taken out together with the upper container 4 while being suspended from the outer ring 6 after being opened as described above. On the other hand, when the upper container 4 moves downward to the original position shown in Fig. 1, the tread molding section 20 moves down to a position adjacent to the lower sidewall molding section 11, and then the outer ring 6 moves downward relative to each intermediate container 5, and each intermediate container 5 moves radially inward around the axis of the tread molding section 20. As a result, as shown in Figs. 1 and 2, each segment 21 is driven by the corresponding intermediate container 5 and moves radially inward together with the intermediate container 5, and the tread molding section 20 is closed to a state where the tire 2 or green tire can be molded.

[0025] As described above, in the tire molding die 1 of this embodiment, the annular tread molding portion 20 is divided into a plurality of segments 21 arranged in the circumferential direction, and each segment 21 is configured to open and close by moving radially.

[0026] The opening and closing mechanism for the tread molding portion 20 is not limited to a configuration using the outer ring 6, and various configurations can be adopted.

[0027] The tire molding mold 1 is disposed inside the green tire and includes a bladder 7 that expands when pressurized steam is supplied thereto. The tire molding mold 1 also includes a heater (not shown) for heating the sidewall molding portion 10 and the tread molding portion 20. The heater can be installed at an appropriate location.

[0028] As shown in FIGS. 5 and 6, in the tire molding die 1 of this embodiment, the plurality of segments 21 constituting the tread molding portion 20 each have a design surface divided mold portion 23.

[0029] In this embodiment, each segment 21 has a holder 22, and the design surface divided mold part 23 is arranged radially inside the holder 22 and fixed to the holder 22 using a fixing member such as a bolt not shown.

[0030] The holder 22 is a part that is driven radially outward by the intermediate container 5 when the tread molding section 20 is opened. The holder 22 is driven radially inward by the intermediate container 5 when the tread molding section 20 is closed. The holder 22 can be formed by cutting a block made of metal such as low carbon steel.

[0031] The design surface divided mold part 23 is a part that constitutes the tread design surface 20a that molds the tread 2c of the tire 2. As shown in Fig. 6, the design surface divided mold part 23 is arc-shaped in a plan view, and the surface facing radially inward constitutes a part that is divided in the circumferential direction of the tread design surface 20a.

[0032] As shown in Fig. 5, the design surface divided mold part 23 may be configured such that the tread design surface 20a is provided with a plurality of protrusions 24 that protrude radially from the tread design surface 20a toward the radially inward direction. The plurality of protrusions 24 are used to form grooves or sipes that form a tread pattern in the tread 2c of the tire 2 during vulcanization molding. The plurality of protrusions 24 may be of various shapes or large (length) sizes corresponding to the tread pattern, such as those that extend in the tire width direction or those that extend in the tire circumferential direction. Note that the tread design surface 20a may not be provided with the protrusions 24.

[0033] The design surface divided mold part 23 is preferably formed by casting a metal material with high thermal conductivity, such as an aluminum alloy. In this case, for example, a rib-shaped or blade-shaped protrusion 24 made of steel may be integrally formed with the design surface divided mold part 23 when the design surface divided mold part 23 is cast.

[0034] The design surface divided mold section 23 is configured to rotate about a rotation axis 25 perpendicular to both the movement direction of the segment 21 and the axis (central axis O) of the tread molding section 20 when the tread molding section 20 is opened after the tire 2 is vulcanized and molded.

[0035] In this embodiment, the holder 22 is rotatably supported in the intermediate container 5 by a rotation axis 25 that is perpendicular to both the movement direction of the segment 21 and the axis of the tread molding portion 20 (parallel to the tangent direction of the tire 2), and the design surface divided mold portion 23 is configured to rotate together with the holder 22 relative to the intermediate container 5 around the rotation axis 25.

[0036] In addition, in this embodiment, the rotating shaft 25 is positioned radially outward from the radial center position of the holder 22, and biased to one side in the axial direction (upper side in Figure 5) from the center position in the axial direction of the tread molding portion 20 of the holder 22.

[0037] More specifically, as shown in Fig. 5 and Fig. 6, a recess 22a is provided at the upper end of the back surface of the holder 22 facing radially outward. Meanwhile, a convex portion 5b protruding radially inward is integrally provided at the upper end of the surface of the intermediate container 5 facing radially inward, and the convex portion 5b is disposed inside the recess 22a. The rotating shaft 25 penetrates the convex portion 5b disposed inside the recess 22a with both ends supported by the holder 22. Thus, the holder 22 is supported by the rotating shaft 25 penetrating the convex portion 5b of the intermediate container 5 at the recess 22a, and is rotatable relative to the intermediate container 5.

[0038] With this configuration, when the tread molding section 20 is opened after the tire 2 is vulcanized, the holder 22 and the design surface divided mold section 23 are rotated relative to the intermediate container 5 about the rotation shaft 25 perpendicular to the movement direction of the segment 21 and the axis of the tread molding section 20 so that the lower end side moves radially inward from a specified position relative to the upper end side where the rotation shaft 25 is provided. Note that the specified position is a position where the design surface divided mold section 23 is in a posture where the tread design surface 20a provided therein is continuously connected to the tread design surface 20a provided on the design surface divided mold section 23 of the other segment 21 along the circumferential direction.

[0039] The tread molding sections 20 are mounted between the corresponding holders 22 and the intermediate containers 5 to hold the corresponding design surface divided mold sections 23 at a specified position, and can be configured to have a spring member 27 that elastically deforms to allow the holders 22 to rotate relative to the intermediate container 5 when the tread molding sections 20 are opened. As shown in Fig. 7, in this embodiment, a bolt 28 is fixed to the back surface of the holder 22, and the spring member 27 is disposed between a head 28a of the bolt 28 disposed in a hole 5c provided in the intermediate container 5 and the bottom wall of the hole 5c of the intermediate container 5. The spring member 27 is a compression coil spring. The spring member 27 biases the portion of the holder 22 away from the pivot axis 25 in a direction toward the intermediate container 5, thereby holding the design surface divided mold portion 23 fixed to the holder 22 in a specified position together with the holder 22, and when the tread molding portion 20 is opened, it elastically deforms between the head 28a of the bolt 28 and the bottom wall of the hole portion 5c, allowing the design surface divided mold portion 23 fixed to the holder 22 to rotate relative to the intermediate container 5.

[0040] Next, a method for producing a tire 2 having a predetermined shape by vulcanizing a green tire using the tire molding mold 1 having the above-mentioned configuration, that is, a tire manufacturing method according to one embodiment of the present invention, will be described.

[0041] First, the sidewall molding section 10 and the tread molding section 20 are opened and a green tire is placed inside the tire molding die 1, and then the sidewall molding section 10 and the tread molding section 20 are closed.

[0042] Next, pressurized steam is supplied to the bladder 7 placed inside the green tire to expand the bladder 7, and both sidewalls of the green tire are pressed against the lower sidewall design surface 11a and the upper sidewall design surface 12a of the sidewall molding portion 10, respectively, and the tread is pressed against the tread design surface 20a of the tread molding portion 20. Then, in this state, the sidewall molding portion 10 and the tread molding portion 20 are heated by a heater, and the synthetic rubber that constitutes the green tire is vulcanized by the heat, and molded into a tire 2 of a predetermined shape.

[0043] After the molding of the tire 2 is completed, the sidewall molding section 10 and the tread molding section 20 are opened, and the molded tire 2 is taken out.

[0044] Here, after the tire 2 has been vulcanized and molded, when each segment 21 moves radially outward to open the tread molding section 20, a driving force is applied to each design surface divided mold section 23 via the holder 22, which resists the adhesion force generated between the tread 2c of the tire 2 and the inner surface of the tread design surface 20a and the undercut resistance generated between the tread 2c of the tire 2 and the protrusion 24. At this time, the design surface divided mold section 23 of each segment 21 is supported on the intermediate container 5 via the holder 22 so that it can rotate freely around the pivot axis 25. Therefore, when the tread molding section 20 is opened after the tire 2 is vulcanized and molded, as shown in Figure 8, the design surface divided mold section 23, together with the holder 22, will spontaneously rotate (pan action) relative to the intermediate container 5 around the pivot axis 25 that is perpendicular to both the movement direction of the segment 21 and the axis of the tread molding section 20, so that the lower end side moves radially inward relative to the upper end side where the pivot axis 25 is provided.

[0045] In this way, in the tire manufacturing method using the tire molding die 1 of the present embodiment, after the tire 2 is vulcanized and molded, when the tread molding section 20 is opened, the tire 2 can be released from the tread molding section 20 while rotating the design surface divided mold section 23 about the rotation axis 25 perpendicular to each of the moving direction of the segment 21 and the axis of the tread molding section 20. As a result, the tread 2c of the tire 2 is gradually released from one end side (upper end side in FIG. 8) of the design surface divided mold section 23 in the width direction of the tire 2 before the other end side (lower end side in FIG. 8), and outside air is gradually introduced between the tread 2c and the tread design surface 20a from the one end side, thereby reducing the release resistance of the tread 2c of the tire 2 from the tread design surface 20a in the early stage of the release of the tire 2. Therefore, in the early stage of demolding of the tire 2, the force required to release the tread 2c of the tire 2 from the tread design surface 20a is reduced, and the driving force required to drive the segments 21 in the early stage of demolding of the tire 2 can be reduced. Also, since the driving force applied to the segments 21 when demolding the tire 2 can be reduced, the overall manufacturing device including the tire molding die 1 can be made smaller, and manufacturing costs can be reduced. Furthermore, since the demolding resistance of the tread 2c of the tire 2 from the tread design surface 20a can be reduced, the occurrence of residual strain (permanent deformation) in the tire 2 after demolding can be suppressed, and the initial performance of the tire 2 can be improved.

[0046] In particular, in this embodiment, the rotating shaft 25 is arranged radially outward from the radial center position of the holder 22 and biased to one side in the axial direction from the center position in the axial direction of the tread molding section 20 of the holder 22, so that the driving force for moving the segments 21 radially outward is applied biased to one end side of the holder 22 or the design surface divided mold section 23 in the width direction of the tire 2, and after the tire 2 is vulcanized and molded, when the tread molding section 20 is opened, the design surface divided mold section 23 can be more reliably rotated spontaneously about the rotating shaft 25. Therefore, the driving force required to drive the segments 21 in the initial stage of demolding of the tire 2 can be more reliably reduced.

[0047] Furthermore, when the tire 2 is released from the tread molding portion 20, each of the design surface divided mold portions 23 rotates about the rotation axis 25, thereby reducing the undercut resistance that the protrusions 24 generate against the tread 2c of the tire 2, and further reducing the driving force required to drive the segments 21 in the initial stage of releasing the tire 2. Furthermore, when the tire 2 is released from the tread molding portion 20, it is possible to prevent the undercut resistance from becoming excessively large, thereby preventing defects such as permanent deformation of the tread 2c of the tire 2 after molding and damage to the protrusions 24.

[0048] Furthermore, in the tire molding die 1 of this embodiment, the tread molding section 20 is mounted between the corresponding holder 22 and intermediate container 5, and holds the corresponding design surface divided mold section 23 in a specified position. Also, when the tread molding section 20 is opened, the spring member 27 is elastically deformed to allow the holder 22 to rotate relative to the intermediate container 5. Therefore, when the raw tire is vulcanized and molded, the design surface divided mold section 23 is reliably held in a specified position, improving the moldability of the tire 2, and after the tire 2 is vulcanized and molded, when the tread molding section 20 is opened, the design surface divided mold section 23 can spontaneously rotate together with the holder 22 about the rotation axis 25 relative to the intermediate container 5, so that the force required to release the tread 2c of the tire 2 from the tread design surface 20a can be more reliably reduced at the beginning of the release of the tire 2.

[0049] The present invention is not limited to the above-described embodiment, and it goes without saying that various modifications can be made without departing from the spirit and scope of the present invention.

[0050] For example, in the above embodiment, a holder 22 is provided on each segment 21, the design surface divided mold part 23 is fixed to the holder 22, and the holder 22 is supported so as to be freely rotatable on the intermediate container 5 by a rotating shaft 25. However, it is also possible to configure the design surface divided mold part 23 to be supported on the intermediate container 5 by the rotating shaft 25 without providing the holder 22.

[0051] Furthermore, the position of the pivot axis 25 can be changed in various ways as long as the design surface divided mold section 23 is configured to spontaneously rotate around the pivot axis 25 when the tread molding section 20 is opened after the tire 2 is vulcanized and molded. [Explanation of symbols]

[0052] 1: tire molding die, 2: tire, 2a: sidewall, 2b: sidewall, 2c: tread, 3: lower container, 4: upper container, 5: intermediate container, 5a: tapered surface, 5b: convex portion, 5c: hole portion, 6: outer ring, 6a: tapered surface, 7: bladder, 10: sidewall molding portion, 11: lower sidewall molding portion, 11a: lower sidewall design surface, 12: upper sidewall molding portion, 12a: upper sidewall design surface, 20: tread molding portion, 20a: tread design surface, 21: segment, 22: holder, 22a: recess, 23: design surface division die portion, 24: protrusion, 25: pivot shaft, 27: spring member, 28: bolt, 28a: head, O: central axis

Claims

1. A tire molding die for vulcanizing and molding an unvulcanized raw tire into a tire, the tire mold comprising an annular tread molding section that is divided into a plurality of segments arranged in a circumferential direction and that is configured to open and close by moving each of the segments in a radial direction, the tire mold comprising: Each of the segments is a design surface division mold part that is provided with a tread design surface for forming a tread of the tire, and that is configured to rotate about a rotation axis perpendicular to each of the moving direction of the segment and the axis of the tread molding part when the tread molding part is opened after the tire is vulcanized and molded; Each of the segments is A container for accommodating a tire or a holder, the container moving radially outward when the tread molding portion is opened; a holder that is driven radially outward by the container when the tread mold portion is opened, The design surface divided mold part is fixed to the radially inner side of the holder, The holder is rotatably supported on the container by the rotation shaft, a spring member which is attached between the corresponding holder and container, holds the corresponding design surface divided mold section in a specified position by biasing the holder in a direction that attracts the holder to the container, and elastically deforms to allow the holder to rotate relative to the container when the tread molding section is opened.

2. 2. The tire molding mold according to claim 1, wherein the pivot shaft is disposed radially outward from a radial center position of the holder and biased to one side in the axial direction from a center position of the holder in the axial direction of the tread molding portion.

3. A tire manufacturing method for manufacturing a tire by vulcanizing and molding an unvulcanized raw tire using a tire molding die having an annular tread molding portion that is divided into a plurality of segments arranged in a circumferential direction and that is configured to open and close by moving each of the segments in a radial direction, the method comprising the steps of: When each of the segments is moved radially outward to open the tread molding portion, the tire is released from the tread molding portion while rotating a design surface division mold portion provided on the segment about a rotation axis perpendicular to each of the moving direction of the segment and the axis of the tread molding portion, and The tire molding mold includes: Each of the segments is A container for accommodating a tire or a holder, the container moving radially outward when the tread molding portion is opened; a holder that is driven radially outward by the container when the tread mold portion is opened, The design surface divided mold part is fixed to the radially inner side of the holder, The holder is rotatably supported on the container by the rotation shaft, a spring member that is attached between the corresponding holder and container, holds the corresponding design surface divided mold section in a specified position by biasing the holder in a direction that attracts the holder to the container, and elastically deforms to allow the holder to rotate relative to the container when the tread molding section is opened.

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