Tire manufacturing method

Abstract

To provide a tire manufacturing method capable of preventing a tire from deforming on removing the tire from a vulcanization mold while reducing pressure of a bladder in vacuum vulcanization.SOLUTION: A method includes: vulcanization step S3 of injecting a hot pressurized medium to an inside of a bladder 3 while an inside of a container 11 is kept under reduced pressure for vulcanization of a tire T; and mold opening step S4 of opening a vulcanization mold 2 while the bladder 3 is kept under reduced pressure. After completion of injecting the hot pressurized medium to the inside of the bladder 3, an atmosphere conduction of conducting an atmosphere between at least the bladder 3 and the tire is performed, and this atmosphere conduction is performed before an inner pressure of the bladder 3 becomes a negative pressure.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a tire manufacturing method capable of preventing deformation of a tire caused by decompressing a bladder when the vulcanized tire is removed from a vulcanization mold. [Background technology]

[0002] A method has been proposed in the past in which, when vulcanizing a tire, the air between the vulcanization mold and the tire is evacuated to the outside by a vacuum means, thereby preventing a deterioration in the appearance quality of the tire due to air accumulation (for convenience, this is sometimes referred to as "vacuum vulcanization") (see, for example, Patent Document 1).

[0003] The vulcanizing device used in the above Patent Document 1 includes a vulcanizing mold, a container capable of enclosing the vulcanizing mold in a sealed state, and a bladder disposed in the vulcanizing mold. The air in the container is sucked by a pressure reducing means, thereby discharging the air between the vulcanizing mold and the tire to the outside. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 04-197713 Summary of the Invention [Problem to be solved by the invention]

[0005] In the vulcanizing device, the tire is vulcanized by injecting a heating and pressurizing medium into the bladder while the inside of the container is in a depressurized state. When the vulcanized tire is removed from the vulcanizing mold, the bladder is depressurized and pulled out from the tire.

[0006] However, in the vulcanization device used in "vacuum vulcanization", the inside of the container is highly airtight. Therefore, as shown by the dashed line in Figure 7, when the pressure of the bladder a is reduced, a vacuum is created between the bladder a and the tire t, causing a problem that the tire t, especially the tread part ta, deforms to fit the bladder a. Such deformation can cause tire vibrations, etc.

[0007] An object of the present invention is to provide a tire manufacturing method capable of preventing deformation of a tire when the tire is removed from a vulcanization mold by reducing the pressure in a bladder during vacuum vulcanization. [Means for solving the problem]

[0008] The present invention provides a tire manufacturing method for vulcanizing an unvulcanized tire using a vulcanization device including a vulcanization mold, a container, and a bladder, comprising: a mold closing process of closing the open vulcanization mold in which the tire has been placed, while surrounding it with the container; a vulcanization step of injecting a heating and pressurizing medium into the bladder under a reduced pressure inside the container to vulcanize the tire; and a mold opening step of discharging the heating and pressurizing medium from the bladder and opening the vulcanization mold in a decompressed state of the bladder, After the completion of injection of the heating and pressurizing medium into the bladder, air communication is performed to communicate at least between the bladder and the tire with the atmosphere.

[0009] The bladder is preferably vented to the atmosphere before the internal pressure of the bladder becomes negative.

[0010] In the tire manufacturing method according to the present invention, the communication with the atmosphere is preferably performed by connecting the inside of the container to the atmosphere.

[0011] In the tire manufacturing method according to the present invention, it is preferable that the vulcanizing mold has a flow path communicating between the bladder and the tire. Effect of the Invention

[0012] The present invention includes a vulcanization process in which a heated and pressurized medium is injected into a bladder under reduced pressure inside a container to vulcanize the tire. This allows the air between the vulcanization mold and the tire to be evacuated and vulcanized, preventing a decrease in appearance quality due to air pockets.

[0013] In addition, in the present invention, after the completion of injection of the heating and pressurizing medium into the bladder, at least the space between the bladder and the tire is connected to the atmosphere, thereby preventing deformation of the tire when the bladder is decompressed and pulled out from the tire. [Brief description of the drawings]

[0014] [Figure 1] 1 is a cross-sectional view showing an embodiment of a vulcanizer used in a tire manufacturing method of the present invention. [Diagram 2] FIG. 2 is an enlarged cross-sectional view showing a main part of the vulcanizing device. [Diagram 3] FIG. 2 is an enlarged cross-sectional view showing a flow path of a vulcanizing mold. [Figure 4] 5(a) to 5(c) are cross-sectional views showing a tire inserting step and a mold closing step. [Diagram 5] 4(a) and 4(b) are cross-sectional views showing a vulcanization step and a mold opening step. [Figure 6] FIG. 11 is a cross-sectional view showing the effect of air conduction. [Figure 7] FIG. 11 is a partial cross-sectional view illustrating a problem in the conventional art. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, an embodiment of the present invention will be described in detail. 1 is a cross-sectional view showing an embodiment of a vulcanizing apparatus 1 used in a tire manufacturing method of the present invention. In FIG. 1, the vulcanizing apparatus 1 of the present embodiment includes a vulcanizing mold 2, a container 11, and a bladder 3.

[0016] The vulcanization mold 2 has a lower mold section 2L attached to a lower plate 4, and an upper mold section 2U attached to an upper plate 5 that can be raised and lowered. The lower plate 4 is supported, for example, by a table base (not shown) of a press machine. In this example, the upper plate 5 is held by a lifting platform 9 of the press machine via a cylinder 10. Therefore, in this example, the lifting platform 9 itself can be raised and lowered, and the upper plate 5 can be raised and lowered relative to the lifting platform 9. The lower plate 4 and the upper plate 5 are configured to include, for example, a platen plate for heating.

[0017] When the upper plate 5 is raised, the vulcanizing mold 2 is brought into an open state Y1, and an unvulcanized tire T is inserted into the vulcanizing mold 2, and a vulcanized tire is removed. When the upper plate 5 is lowered, the vulcanizing mold 2 is brought into a closed state Y2 (shown in FIG. 2), and vulcanization is performed.

[0018] The lower mold section 2L includes a lower side mold 7L having a surface SL for molding the lower bead portion and the lower sidewall portion of the unvulcanized tire T. The lower mold section 2L may be divided into a mold portion for molding the lower bead portion and a mold portion for molding the lower sidewall portion.

[0019] The upper mold section 2U includes an upper side mold 7U having a surface SU for molding an upper bead portion and an upper sidewall portion of the tire T, and a tread mold 8 having a surface ST for molding a tread portion of the tire T. The upper mold section 2U may be divided into a mold portion for molding an upper bead portion and a mold portion for molding an upper sidewall portion. The tread mold 8 is composed of a plurality of segments 8A divided in the circumferential direction. The upper end portion of each segment 8A is supported by the upper plate 5 so as to be movable in the tire radial direction. In addition, a cylindrical container 11 is attached to the lifting platform 9, which moves each segment 8A radially inward when it descends.

[0020] The surfaces SL, SU, and ST are sometimes collectively referred to as the tire molding surface S.

[0021] The container 11 has a cone-shaped guide surface 11s on its inner circumferential surface, the diameter of which increases toward the bottom. Each segment 8A is slidably held along the guide surface 11s via an appropriate guide means (not shown). Therefore, as the container 11 descends, each segment 8A is pushed by the guide surface 11s and can move radially inward on the lower plate 4 until it reaches the closed state Y2.

[0022] As shown in Fig. 2, in this example, a sealing wall portion 12 is erected on the lower plate 4. This sealing wall portion 12 has a cylindrical shape concentric with the container 11, and seals between itself and the container 11 in the lowered state via a sealing ring 18, such as an O-ring. This makes it possible to hermetically seal the internal space H surrounded by the container 11 and the sealing wall portion 12 in the closed state Y2. The sealing ring 18 may be disposed on the outer circumferential surface of the container 11, or may be disposed on the inner circumferential surface of the sealing wall portion 12. Also, an exhaust hole 19 communicating with the internal space H is formed in the sealing wall portion 12.

[0023] As another embodiment of the sealing wall portion 12, the sealing wall portion 12 may be provided as a part of the container 11 on the outer periphery of the container 11 so as to be slidable up and down. In this case, it is preferable to provide a sealing member at the lower end portion of the sealing wall portion 12 for sealing between the sealing wall portion 12 and the lower plate 4 in the closed state Y2.

[0024] A bladder central mechanism 13 having a bladder 3 is disposed at the center of the vulcanization mold 2. The bladder central mechanism 13 of this example includes the bladder 3, upper and lower clamp rings 14U and 14L, and a center post 15.

[0025] The lower clamp ring 14L holds the lower opening of the bladder 3. This lower clamp ring 14L is supported by the lower plate 4 via the lower mold part 2L. The upper clamp ring 14U holds the upper opening of the bladder 3. This upper clamp ring 14U is attached to the upper end of the center post 15. The center post 15 is attached to the lower plate 4 so that it can be raised and lowered via a lifting means (not shown) such as a cylinder.

[0026] Bladder center mechanism 13 slidably holds center post 15, and further includes a cylindrical portion 16 having an inlet / outlet port 16A through which a heating and pressurizing medium can be supplied to and discharged from bladder 3.

[0027] In this embodiment, an inert gas such as nitrogen gas is used as the heating and pressurizing medium, but a mixed gas of an inert gas and steam may also be used. Furthermore, it is also preferable to use steam and then supply an inert gas following the steam.

[0028] The vulcanizing mold 2 has a first flow path 20 communicating between the bladder 3 and the tire T, and a second flow path 21 communicating between the vulcanizing mold 2 and the tire T.

[0029] As shown in Fig. 3 representatively for the lower mold part 2L, the first flow passage 20 extends through the lower side mold 7L in the tire axial direction. One end 20a of the first flow passage 20 opens on the inner surface in the tire axial direction of the lower side mold 7L and at a position on the inner side in the tire radial direction of the tire than the tire molding surface S. As a result, the first flow passage 20 can be electrically connected between the bladder 3 and the tire T via the gap between the bladder 3 and the lower side mold 7L. The first flow passage 20 is similarly formed in the upper side mold 7U.

[0030] The second flow passage 21 extends through the lower side mold 7L in the tire axial direction. One end 21a of the second flow passage 21 opens at the tire molding surface S. This allows the second flow passage 21 to be electrically connected between the lower side mold 7L and the tire T. The second flow passage 21 is similarly formed in the upper side mold 7U.

[0031] The first and second flow paths 20, 21 are connected to the exhaust hole 19 via a flow path including a flow path 22 between the lower side mold 7L and the lower plate 4, and a flow path 23 between the upper side mold 7U and the upper plate 5, and the internal space H.

[0032] As shown in Fig. 2, the vulcanizing apparatus 1 further includes a pressure reducing means 25 for reducing the pressure in the internal space H. The pressure reducing means 25 includes a vacuum tank 27 that communicates with the exhaust port 19 via a switching valve 26, and a vacuum pump 28 that communicates with the vacuum tank 27. An ON-OFF valve 33 that switches communication with the atmosphere on and off is connected to the switching valve 26. Thus, by operating the switching valve 26 and the ON-OFF valve 33, The exhaust port 19 is connected to the vacuum tank 27 to reduce the pressure in the internal space H; - Maintaining the reduced pressure in the inner space H by blocking the communication: Release the vacuum and open the inner space H to the atmosphere: may be selected.

[0033] In the figure, reference numeral 28 denotes a strainer, reference numeral 29 denotes an ON-OFF valve that switches the communication between the vacuum tank 27 and the vacuum pump 28 on and off, and reference numeral 30 denotes a one-way valve that prevents backflow of air from the vacuum pump 28.

[0034] Next, as shown in FIGS. 4 and 5, the tire manufacturing method includes a tire inserting step S1, a mold closing step S2, a vulcanization step S3, and a mold opening step S4.

[0035] As shown in FIG. 4(a), in the tire loading step S1, in an open state Y1, a previously formed unvulcanized tire T is loaded onto the lower side mold 7L using a known loader (not shown). At the time of loading, the bladder 3 is in a reduced pressure state to avoid contact with the tire T. After loading, the bladder 3 is expanded to a held internal pressure as shown by the dashed line. This supports the tire T from the inside and holds it vertically. The held internal pressure is preferably in the range of 40 to 70 kPa (gauge pressure).

[0036] As shown in Fig. 4(b) and (c), in the mold closing step S2, the vulcanization mold 2 in the open state Y1 into which the tire T has been introduced is closed while being surrounded by the container 11. Specifically, in this example, the lifting platform 9 descends together with the upper plate 5, and the descent of the upper plate 5 ends when the segments 8A reach above the lower plate 4. At this time, the tire T is sandwiched between the lower side mold 7L and the upper side mold 7U. Thereafter, the lifting platform 9 descends further, and the container 11 pushes the segments 8A inward in the tire radial direction. This results in a closed state Y2, and the internal space H surrounded by the container 11 and the sealing wall portion 12 is sealed.

[0037] As shown in Fig. 5(a), in the vulcanization step S3, the pressure reducing means 25 is operated to reduce the pressure of the internal space H in the container 11. In this reduced pressure state, a heating and pressurizing medium is injected into the bladder 3 to vulcanize the tire T. Note that the pressure reduction may start when the container 11 is lowered and the internal space H is sealed. Also, after the pressure reduction has started, the injection of the heating and pressurizing medium into the bladder 3 may start before the pressure reduction is completed.

[0038] As the pressure is reduced, the air between the tire T and the vulcanization mold 2 is forcibly exhausted to the outside via the second flow path 21. Similarly, as the pressure is reduced, the air between the tire T and the bladder 3 is also forcibly exhausted to the outside via the first flow path 20. This prevents air from being trapped, and suppresses deterioration in the appearance quality of the tire.

[0039] As shown in FIG. 5(b), in the mold-opening process S4, the heating and pressurizing medium is discharged from the bladder 3 and the bladder 3 is depressurized (under negative pressure), i.e., the bladder 3 is pulled out from the vulcanized tire T1, and the vulcanization mold 2 is opened.

[0040] In the tire manufacturing method, after (including) completion of injection of the heated and pressurized medium into the bladder 3, air communication is performed to connect at least the space between the bladder 3 and the tire T to the atmosphere. In this example, this air communication is performed by operating the switching valve 26 and the ON-OFF valve 33 to release the reduced pressure in the internal space H and connect the internal space H to the atmosphere.

[0041] 6, when the pressure in the bladder 3 is reduced in the mold opening step S4, the air E can be sent between the bladder 3 and the tire T1 from the first flow path 20. As a result, deformation of the tire T1 can be prevented when the bladder 3 is pulled out from the vulcanized tire T1.

[0042] For the atmospheric communication, a separate flow path may be provided that communicates between the bladder 3 and the tire T but is independent of the internal space H, and only the space between the bladder 3 and the tire T may be communicated with the atmosphere.

[0043] This air connection may be performed during vulcanization after the completion of injection of the heating and pressurizing medium. Note that, in order to prevent deformation of the tire T1, it is preferable to perform the air connection before the internal pressure of the bladder 3 becomes negative. In other words, even if the heating and pressurizing medium is being discharged from the bladder 3, the air connection can be performed until the internal pressure of the bladder 3 switches from 0 to negative.

[0044] Although a particularly preferred embodiment of the present invention has been described in detail above, the present invention is not limited to the illustrated embodiment and can be modified in various ways. EXAMPLES

[0045] In order to confirm the effect of the present invention, 30 tires of each size 235 / 60R were manufactured by vacuum vulcanization based on the specifications in Table 1 using a vulcanizing device having the structure shown in Fig. 2. All tires (30 of each type) were then visually checked for defects due to remaining air in the tires and for the occurrence of tire deformation defects when the bladder was pulled out. If there were zero defective tires, it was marked as "absent," and if there was one or more defective tires, it was marked as "present."

[0046] The conventional example, comparative example, and working example have substantially the same specifications, except for the presence or absence of air conduction and the timing of air conduction.

[0047] [Table 1] [Explanation of symbols]

[0048] 1 Vulcanizing equipment 2 Vulcanization mold 3. Bladder 11 Container 20 Flow Path S2 Mold closing process S3 Vulcanization process S4 Mold opening process T Tire

Claims

1. A tire manufacturing method for vulcanizing an unvulcanized tire using a vulcanization device including a vulcanization mold, a container, and a bladder, comprising: a mold closing process of closing the open vulcanization mold in which the tire has been placed, while surrounding it with the container; a vulcanization step of injecting a heating and pressurizing medium into the bladder under a reduced pressure inside the container to vulcanize the tire; and a mold opening step of discharging the heating and pressurizing medium from the bladder and opening the vulcanization mold in a decompressed state of the bladder, After the injection of the heating and pressurizing medium into the bladder is completed, the reduced pressure inside the container is released and an atmosphere is communicated between at least the bladder and the tire, The venting to the atmosphere is performed before the internal pressure of the bladder becomes negative. Tire manufacturing method.

2. The tire manufacturing method according to claim 1 , wherein the air communication is performed by connecting the inside of the container to the atmosphere.

3. The tire manufacturing method according to claim 1 or 2, wherein the vulcanization mold has a flow passage communicating between the bladder and the tire.

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