JP7613075B2 - Tire manufacturing method - Google Patents

Description

The present invention relates to a tire manufacturing method that can prevent deformation of a tire caused by decompressing a bladder when removing the vulcanized tire from a vulcanization mold.

A method has been proposed in the past in which the air between the vulcanization mold and the tire is exhausted to the outside by a vacuum means when vulcanizing a tire, thereby preventing deterioration of the tire's appearance quality due to air pockets (for convenience, this is sometimes called "vacuum vulcanization") (see, for example, Patent Document 1).

The vulcanizing device used in the above-mentioned Patent Document 1 comprises a vulcanizing mold, a container capable of enclosing the vulcanizing mold in a sealed state, and a bladder disposed within the vulcanizing mold. The air within the container is then sucked out by a pressure reducing means, thereby discharging the air between the vulcanizing mold and the tire to the outside.

JP 04-197713

In the vulcanizing device, the tire is vulcanized by injecting a heated and pressurized medium into the bladder while the inside of the container is depressurized. When the vulcanized tire is removed from the vulcanizing mold, the bladder is depressurized and pulled out from the tire.

However, in the vulcanization equipment used in "vacuum vulcanization," the inside of the container is highly airtight. Therefore, as shown by the dashed line in Figure 7, when the bladder a is depressurized, a vacuum is created between the bladder a and the tire t, causing the tire t, and especially the tread portion ta, to deform to fit the bladder a. Such deformation can cause tire vibrations, etc.

The objective of the present invention is to provide a tire manufacturing method that can prevent deformation of a tire during vacuum vulcanization when the bladder is depressurized and the tire is removed from the vulcanization mold.

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 injection of the heating and pressurizing medium into the bladder is completed, air communication is performed to communicate at least between the bladder and the tire with the atmosphere.

It is also preferable that the atmospheric connection be performed before the internal pressure of the bladder becomes negative.

In the tire manufacturing method according to the present invention, the air connection is preferably achieved by connecting the inside of the container to the atmosphere.

In the tire manufacturing method according to the present invention, it is preferable that the vulcanization mold has a flow path between the bladder and the tire.

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 deterioration in appearance quality due to air pockets.

In addition, in the present invention, after the injection of the heated and pressurized medium into the bladder is completed, at least the space between the bladder and the tire is connected to the atmosphere. This makes it possible to prevent the tire from being deformed when the bladder is depressurized and pulled out of the tire.

1 is a cross-sectional view showing an embodiment of a vulcanizer used in a tire manufacturing method of the present invention. FIG. 2 is an enlarged cross-sectional view showing a main part of the vulcanizing device. FIG. 2 is an enlarged cross-sectional view showing a flow path of a vulcanizing mold. 5A to 5C are cross-sectional views showing a tire inserting step and a mold closing step. 4A and 4B are cross-sectional views showing a vulcanization step and a mold opening step. FIG. 11 is a cross-sectional view showing the effect of air conduction. FIG. 11 is a partial cross-sectional view illustrating a problem in the conventional art.

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 the 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.

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, on a table base (not shown) of a press machine. In this example, the upper plate 5 is held on 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.

When the upper plate 5 rises, the vulcanizing mold 2 is in the open state Y1, and unvulcanized tires T are inserted into the vulcanizing mold 2 and vulcanized tires are removed. When the upper plate 5 descends, the vulcanizing mold 2 is in the closed state Y2 (shown in Figure 2) and vulcanization is performed.

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.

The upper mold section 2U includes an upper side mold 7U having a surface SU for molding the upper bead portion and the upper sidewall portion of the tire T, and a tread mold 8 having a surface ST for molding the tread portion of the tire T. The upper mold section 2U may be divided into a mold portion for molding the upper bead portion and a mold portion for molding the 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.

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

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 held slidably 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.

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 it 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 peripheral surface of the container 11, or may be disposed on the inner peripheral surface of the sealing wall portion 12. An exhaust hole 19 that leads to the internal space H is formed in the sealing wall portion 12.

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

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

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 section 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.

The bladder center mechanism 13 slidably holds the center post 15 and further includes a tubular portion 16 with a supply/discharge port 16A through which the heated/pressurized medium can be supplied and discharged into the bladder 3.

In this example, an inert gas such as nitrogen gas is used as the heating and pressurizing medium. However, a mixture of an inert gas and steam may also be used, and it is also preferable to use steam and then supply the inert gas after the steam.

The vulcanization mold 2 has a first flow path 20 that connects between the bladder 3 and the tire T, and a second flow path 21 that connects between the vulcanization mold 2 and the tire T.

As shown in FIG. 3 as a representative example of 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 of the lower side mold 7L in the tire axial direction and at a position radially inward of the tire molding surface S. This allows the first flow passage 20 to 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.

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.

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

As shown in Fig. 2, the vulcanizing apparatus 1 further includes a pressure reducing means 25 for reducing the pressure of 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 internal space H is depressurized by connecting the exhaust hole 19 to the vacuum tank 27;
By blocking communication, the reduced pressure in the internal space H is maintained:
Release the vacuum and open the inner space H to the atmosphere:
may be selected.

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, and reference numeral 30 denotes a one-way valve that prevents backflow of air from the vacuum pump 28.

Next, the tire manufacturing method includes a tire inserting process S1, a mold closing process S2, a vulcanization process S3, and a mold opening process S4, as shown in Figures 4 and 5.

As shown in FIG. 4(a), in the tire loading step S1, in the open state Y1, a preformed unvulcanized tire T is loaded onto the lower side mold 7L using a well-known loader (not shown). When 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 the held internal pressure as shown by the dashed and dotted line. This supports the tire T from the inside and holds it vertically. A range of 40 to 70 kPa (gauge pressure) is suitable as the held internal pressure.

As shown in Figures 4(b) and (c), in the mold closing step S2, the vulcanization mold 2 in the open state Y1 with the tire T inserted therein 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 segment 8A reaches 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 segment 8A radially inward in the tire 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.

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.

As the pressure is reduced, the air between the tire T and the vulcanization mold 2 is forcibly exhausted to the outside through the second flow path 21. Similarly, as the pressure is reduced, the air between the tire T and the bladder 3 is forcibly exhausted to the outside through the first flow path 20. This prevents air from pooling and suppresses deterioration of the appearance quality of the tire.

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

In addition, in the tire manufacturing method, after (including at) the completion of injection of the heated and pressurized medium into the bladder 3, an atmosphere connection is established between at least the bladder 3 and the tire T to the atmosphere. In this example, this atmosphere connection is established 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.

As a result, as shown in FIG. 6, when the bladder 3 is depressurized in the mold opening process 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.

For atmospheric communication, a separate flow path may be provided between the bladder 3 and the tire T but independent of the internal space H, so that only the space between the bladder 3 and the tire T is connected to the atmosphere.

This atmospheric connection may be performed during vulcanization after the completion of injection of the heating and pressurizing medium. To prevent deformation of the tire T1, it is preferable to perform this before the internal pressure of the bladder 3 becomes negative. In other words, even if the heating and pressurizing medium is in the process of being exhausted from the bladder 3, atmospheric connection can be performed until the internal pressure of the bladder 3 switches from 0 to negative.

The above describes in detail a particularly preferred embodiment of the present invention, but the present invention is not limited to the illustrated embodiment and can be modified and implemented in various ways.

To confirm the effect of the present invention, 30 tires of each size 235/60R were manufactured by vacuum vulcanization using a vulcanizing device having the structure shown in Figure 2 and based on the specifications in Table 1. 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 removed. 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."

The conventional example, comparative example, and working example have substantially the same specifications, except for the presence or absence of atmospheric conductivity and the timing of atmospheric conductivity.

1 Vulcanization device 2 Vulcanization mold 3 Bladder 11 Container 20 Flow path S2 Mold closing process S3 Vulcanization process S4 Mold opening process T Tire

Claims (3)

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. The tire manufacturing method according to claim 1, wherein the air connection is achieved by connecting the inside of the container to the atmosphere. The tire manufacturing method according to claim 1 or 2, wherein the vulcanization mold has a flow path between the bladder and the tire.

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