JP2023091335A - Tire manufacturing method - Google Patents

Abstract

To provide a tire manufacturing method in which clogging of a vent hole due to spew can effectively be suppressed.SOLUTION: Using a mold 10 having a molding surface 31 for molding tire outer surface and a vent hole 32 opened in the molding surface 31, an unvulcanized-state tire T is placed inside the mold 10, and, by vulcanizing the tire T while pressurizing toward the molding surface 31, a plurality of tires T are repetitively manufactured. A first vulcanization process for vulcanizing the tire T at a reference internal pressure at the initial stage of vulcanization and a second vulcanization process for vulcanizing the tire T at an internal pressure higher than the reference internal pressure at the initial stage of vulcanization are set. Alternatively, a first vulcanization process for vulcanizing the tire T without manipulating the inner wall temperature of the vent hole 32 before the start of vulcanization, and a second vulcanization process for vulcanizing the tire T in a state of lowered temperature of the vent hole 32 before the start of vulcanization are set. The second vulcanization process is performed at arbitrary frequency for the first vulcanization process.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a tire using a tire vulcanization mold provided with vent holes, and more particularly to a method for manufacturing a tire capable of effectively suppressing clogging of the vent holes due to spew. .

In the manufacturing process of a pneumatic tire, an unvulcanized tire is placed inside a tire vulcanizing mold, and the tire is vulcanized by heating the tire while pressurizing it from the inside with a bladder. . At that time, if air remains between the molding surface of the tire vulcanizing mold and the unvulcanized tire, the residual air causes tire surface failure. In order to prevent such tire surface failures, a tire vulcanizing mold is provided with a large number of air vent holes that open to the molding surface (see, for example, Patent Document 1).

However, if at least part of the spew (whisker-like rubber pieces) formed in the vent hole during vulcanization remains in the vent hole during mold release and clogs the vent hole, the vent hole may be clogged in the next vulcanization. Air can not be removed by holes, and tire surface failure will occur in that portion. In addition, when the spew clogs the vent hole, it is necessary to temporarily stop the production of tires to clean the vent hole, which is a factor that greatly reduces the productivity of the tire.

JP 2012-139830 A

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a tire that makes it possible to effectively suppress clogging of vent holes due to spew.

A tire manufacturing method (first method) of the present invention for achieving the above object is to provide a tire vulcanization mold having a molding surface for molding the tire outer surface and a vent hole opening to the molding surface. An unvulcanized tire is placed inside the tire vulcanizing mold and vulcanized while pressing the tire against the molding surface to repeatedly manufacture a plurality of tires. In the method
A first vulcanization process for vulcanizing the tire at a reference internal pressure in the initial stage of vulcanization, and a second vulcanization process for vulcanizing the tire at an internal pressure higher than the reference internal pressure at the initial stage of vulcanization, The second vulcanization process is performed at any frequency with respect to the first vulcanization process.

In addition, a tire manufacturing method (second method) of the present invention for achieving the above object is a tire vulcanizer having a molding surface for molding the tire outer surface and a vent hole opening in the molding surface. Using a mold, an unvulcanized tire is put inside the tire vulcanizing mold, and the tire is vulcanized while being pressed against the molding surface, so that a plurality of tires are repeatedly formed. In the method of manufacturing
A first vulcanization process in which the tire is vulcanized without manipulating the inner wall temperature of the vent hole before the start of vulcanization; and a second vulcanization process for vulcanization, wherein the second vulcanization process is performed at any frequency with respect to the first vulcanization process.

As a result of intensive research on a method for manufacturing a tire using a tire vulcanization mold provided with vent holes, the present inventor found that when vulcanization is repeated using such a tire vulcanization mold, We recognize the phenomenon that dirt gradually accumulates near the tip of the formed spew, and the tip of the spew breaks due to the deposits. The present inventors have found that clogging can be effectively suppressed, leading to the present invention.

That is, the first method of the present invention includes a first vulcanization process in which the tire is vulcanized at a reference internal pressure at the initial stage of vulcanization, and a second vulcanization process in which the tire is vulcanized at an internal pressure higher than the reference internal pressure at the initial stage of vulcanization. vulcanization process, wherein the second vulcanization process is performed with any frequency with respect to the first vulcanization process. In the first vulcanization process, dirt accumulates near the tip of the spew formed in the vent hole. By vulcanizing, the spew becomes longer than the spew formed in the first vulcanization process, and the dirt deposited near the tip of the spew in the first vulcanization process is replaced by the spew formed in the second vulcanization process. can be wiped out by pulling out the This prevents dirt from accumulating near the tip of the spew, prevents breakage of the tip of the spew caused by such deposits, and effectively suppresses clogging of the vent hole by the spew. can be done. As a result, it is possible to prevent damage to the tire surface caused by residual air, reduce the frequency of vent hole cleaning, and improve tire productivity.

In the first method of the present invention, when the tire is vulcanized, the inside of the tire is filled with the heating medium, and then the pressurized medium is filled. It is preferable to start charging the pressurized medium earlier than the first vulcanization process. By such operation, the first vulcanization process and the second vulcanization process can be easily performed.

In the first method of the present invention, the frequency of the second vulcanization process to the first vulcanization process is preferably 1/10 to 1/30. By performing the second vulcanization process at such a frequency, clogging of the vent holes due to spew can be effectively suppressed.

On the other hand, the second method of the present invention includes the first vulcanization process in which the tire is vulcanized without manipulating the inner wall temperature of the vent hole before the start of vulcanization, and and a second vulcanization process for vulcanizing the tire in a reduced state, with the second vulcanization process being performed with any frequency relative to the first vulcanization process. In the first vulcanization process, dirt accumulates near the tip of the spew formed in the vent hole, while in the second vulcanization process, the inner wall temperature of the vent hole is lowered before vulcanization starts. By vulcanizing the tire in this state, the spew is longer than the spew formed in the first vulcanization process, and dirt deposited near the tip of the spew in the first vulcanization process is removed by the second vulcanization process. can be swept out by withdrawal of the spew formed in the This prevents dirt from accumulating near the tip of the spew, prevents breakage of the tip of the spew caused by such deposits, and effectively suppresses clogging of the vent hole by the spew. can be done. As a result, it is possible to prevent damage to the tire surface caused by residual air, reduce the frequency of vent hole cleaning, and improve tire productivity.

In the second method of the present invention, it is preferable to lower the inner wall temperature of the vent hole by causing air to flow through the vent hole before starting vulcanization in the second vulcanization process. By such operation, the first vulcanization process and the second vulcanization process can be easily performed.

In the second method of the present invention, the frequency of the second vulcanization process to the first vulcanization process is preferably 1/10 to 1/30. By performing the second vulcanization process at such a frequency, clogging of the vent holes due to spew can be effectively suppressed.

1 is a meridian sectional view showing a tire vulcanizer used in the present invention; FIG. FIG. 4 is a cross-sectional view showing a spew formed inside a vent hole of a tire vulcanization mold; FIG. 2 shows a vent hole cleaning mechanism in the tire manufacturing method according to the present invention, and (a) to (b) are cross-sectional views showing the state of the vent hole at each stage. 4 is a graph showing a pressure control program in the tire manufacturing method (first method) according to the present invention. 4 is a graph showing changes in the temperature of the wall surface of the vent hole in the tire manufacturing method (second method) according to the present invention. 4 is a graph showing changes in the degree of vulcanization of the rubber surface layer in the tire manufacturing method (second method) according to the present invention. 4 is a graph showing changes in spew length in the tire manufacturing method (second method) according to the present invention. FIG. 2 shows a clogging generation mechanism in a conventional vent hole, and (a) to (c) are cross-sectional views showing states of the vent hole at each stage.

Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows a tire vulcanizer used in the present invention.

As shown in FIG. 1, this tire vulcanizing apparatus includes a tire vulcanizing mold (hereinafter referred to as "mold") 10 for molding the outer surface of the pneumatic tire T, and a tire vulcanizing mold 10 which is inserted inside the pneumatic tire T. and a cylindrical bladder 20 that is fitted. The tire vulcanizing apparatus also includes heating and pressurizing medium supply means for supplying a heating medium M1 such as steam and a pressurizing medium M2 such as inert gas (for example, nitrogen gas) to the inside of the bladder 20. (not shown) and heating means (not shown) for heating the mold 10 .

The mold 10 includes a lower side plate 11 and an upper side plate 12 for molding the sidewall portion of the pneumatic tire T, and a lower bead ring 13 and an upper bead for molding the bead portion of the pneumatic tire T. It is composed of a ring 14 and a plurality of sectors 15 for molding the tread portion of the pneumatic tire T, and the pneumatic tire T is vulcanized inside the mold 10 . The structure of the mold 10 is not particularly limited, and in addition to the sectional type mold shown in the figure, it is also possible to use a split type mold.

Bladder 20 has its lower end held between lower bead ring 13 and lower clamp ring 21 and its upper end held between upper clamp ring 22 and auxiliary ring 23 . In the vulcanized state as shown in FIG. 1, the bladder 20 expands radially outward of the pneumatic tire T, but when the pneumatic tire T is removed from the mold 10 after vulcanization, The clamp ring 22 moves upward, and the bladder 20 is extracted from the inside of the pneumatic tire T accordingly.

In the tire vulcanizer described above, as shown in FIG. 1, the mold 10 has a molding surface 31 for molding the outer surface of the tire, and a vent hole 32 opening into the molding surface 31 . One end of the vent hole 32 opens to the molding surface 31 and the other end communicates with the outside of the mold 10 . FIG. 1 depicts a structure in which the vent holes 32 are formed in the sectors 15 that make up the mold 10. The vent holes 32 are formed in the lower side plate 11, the upper side plate 12, the lower bead ring 13 or the It is also possible to form in the upper bead ring 14, and it is possible to arrange a large number of vent holes 32 throughout the mold 10. FIG.

When vulcanizing the pneumatic tire T using the tire vulcanizing apparatus described above, the pneumatic tire T in an unvulcanized state is put inside the mold 10, and the bladder 20 is inserted inside the pneumatic tire T. Then, by introducing the heating medium M1 and the pressurizing medium M2 into the bladder 20 and heating the mold 10 from the outside, the pneumatic tire T is pressurized toward the molding surface 31 while the pneumatic tire T is compressed. Vulcanize.

In such a vulcanization process, air remaining between the molding surface 31 of the mold 10 and the unvulcanized pneumatic tire T is discharged to the outside of the mold 10 through the vent holes 32 . Then, the unvulcanized rubber forming the pneumatic tire T intrudes into the vent hole 32, and a spew S is formed in the vent hole 32 as shown in FIG. The spew S is pulled out from the vent hole 32 when the vulcanized pneumatic tire T is removed from the mold 10 . The spew S is then excised as needed.

Here, the clogging mechanism of a conventional vent hole will be described in detail with reference to FIGS. 8(a) to 8(c). First, as shown in FIG. 8(a), when the vulcanization process is repeated, dirt accumulates near the tip of the spew S formed in the vent hole 32 of the mold 10, and the deposit X is gradually removed. grow up. Next, as shown in FIG. 8(b), the unvulcanized rubber G enters the vent hole 32 during vulcanization and reaches a position beyond the deposit X. Then, as shown in FIG. Then, as shown in FIG. 8(c), when the spew S is pulled out after vulcanization, the tip of the spew S integrated with the deposit X is torn off to block the vent hole 32. As shown in FIG.

Therefore, in the present invention, by devising the operation during vulcanization, it is possible to prevent dirt from accumulating in the vicinity of the tip of the spew S formed in the vent hole 32, thereby preventing the opening of the vent hole 32. It effectively prevents clogging.

That is, in the first method, a tire vulcanization mold 10 having a molding surface 31 for molding the tire outer surface and a vent hole 32 opening in the molding surface 31 is used. A plurality of pneumatic tires T are repeatedly manufactured by putting an unvulcanized pneumatic tire T into the inside of the and vulcanizing the pneumatic tire T while pressurizing the pneumatic tire T toward the molding surface 31. In the method, a first vulcanization process in which the pneumatic tire T is vulcanized at the reference internal pressure at the initial stage of vulcanization, and a second vulcanization process in which the pneumatic tire T is vulcanized at an internal pressure higher than the reference internal pressure at the initial stage of vulcanization. and the second vulcanization process is performed at any frequency with respect to the first vulcanization process.

FIG. 3 shows a vent hole cleaning mechanism in the tire manufacturing method according to the present invention, and (a) to (b) show the state of the vent hole at each stage. As shown in FIG. 3(a), in the first vulcanization process, dirt accumulates near the tip of the spew S1 formed in the vent hole 32, and a deposit X is formed. On the other hand, as shown in FIG. 3(b), in the second vulcanization process, the pneumatic tire T is vulcanized at an internal pressure higher than the reference internal pressure at the initial stage of vulcanization, so that the spew S2 is the second It is longer than the spew S1 formed in the first vulcanization process, and the deposit X deposited near the tip of the spew S1 in the first vulcanization process is wiped out by pulling out the spew S2 formed in the second vulcanization process. be able to. That is, the first vulcanization process is a standard vulcanization process, and the second vulcanization process is a vulcanization process that also serves as cleaning work. This prevents dirt from accumulating near the tip of the spew S1, prevents breakage of the tip of the spew S1 due to such deposits X, and effectively suppresses clogging of the vent hole 32. can do. The second vulcanization process does not impair the quality of the pneumatic tire T obtained. Moreover, it is desirable that the spew S2 is longer than the normal spew S1 by 2 mm or more.

FIG. 4 shows a pressure control program in the tire manufacturing method (first method) according to the present invention. In FIG. 4, the horizontal axis is the vulcanization time, and the vertical axis is the internal pressure of the bladder. The solid line in FIG. 4 indicates the pressure change in the first vulcanization process. In the first vulcanization process, first, at the initial stage of vulcanization, the heating medium M1 is introduced into the bladder 20 to set the internal pressure to P1 (reference internal pressure), and then the pressurized medium M2 is introduced into the bladder 20 to increase the internal pressure. Vulcanization is performed by setting it to P2. On the other hand, the dashed line in FIG. 4 indicates the pressure change in the second vulcanization process. Also in the second vulcanization process, first, the heating medium M1 is introduced into the bladder 20 to set the internal pressure to P1, and then the pressurized medium M2 is introduced into the bladder 20 to set the internal pressure to P2. By making the filling start timing of the pressurized medium M2 in the vulcanization process earlier than the filling start timing of the pressurized medium M2 in the first vulcanization process, the internal pressure P2 is made higher than the reference internal pressure P1 at the initial stage of vulcanization.

By adopting the pressure control program as described above, the spew S2 formed in the second vulcanization process becomes longer than the spew S1 formed in the first vulcanization process, and the spew S1 in the first vulcanization process Dirt that accumulates near the tip can be cleaned by pulling out the spew S2 formed in the second vulcanization process.

In the first method described above, the initial vulcanization period is a period in which vulcanization of the pneumatic tire T has not sufficiently progressed. It is a period until In the second vulcanization process, an internal pressure P2 higher than the reference internal pressure P1 may be applied at least partially in the initial stage of vulcanization.

In the first method described above, the internal pressure P1 (reference internal pressure) is set based on the heating medium M1, and the pressure is adjusted based on the pressurizing medium M2. has little effect on That is, when the pressure of the second vulcanization process is adjusted based on the heating medium M1, the temperature changes accordingly. , does not cause such inconvenience.

In addition, in the first method described above, the case where the heating medium M1 and the pressurizing medium M2 are filled in the bladder 20 has been described, but it is also possible to use other media. For example, in the case of hot water vulcanization in which the bladder 20 is filled with hot water, it is possible to adjust the pressure of the hot water.

Next, the second method will be explained. In the second method, a tire vulcanization mold 10 having a molding surface 31 for molding the tire outer surface and a vent hole 32 opening in the molding surface 31 is used, and the inside of the tire vulcanization mold 10 A method for repeatedly manufacturing a plurality of pneumatic tires T by putting an unvulcanized pneumatic tire T into the molding surface 31 and vulcanizing the pneumatic tire T while pressurizing it toward the molding surface 31. , a first vulcanization process in which the pneumatic tire T is vulcanized without manipulating the inner wall temperature of the vent hole 32 before the start of vulcanization; A second vulcanization process for vulcanizing the pneumatic tire T is provided, and the second vulcanization process is performed with arbitrary frequency with respect to the first vulcanization process.

Also in this case, as in the method described above, as shown in FIG. X is formed. On the other hand, as shown in FIG. 3B, in the second vulcanization process, the pneumatic tire T is vulcanized while the temperature of the inner wall of the vent hole 32 is lowered before vulcanization is started. , the progress of cross-linking slows down, the spew S2 becomes longer than the spew S1 formed in the first vulcanization process, and the deposit X deposited near the tip of the spew S1 in the first vulcanization process becomes the second It can be swept away by withdrawal of the spew S2 formed in the vulcanization process. That is, the first vulcanization process is a standard vulcanization process, and the second vulcanization process is a vulcanization process that also serves as cleaning work. This prevents dirt from accumulating near the tip of the spew S1, prevents breakage of the tip of the spew S1 due to such deposits X, and effectively suppresses clogging of the vent hole 32. can do. The second vulcanization process does not impair the quality of the pneumatic tire T obtained. Moreover, it is desirable that the spew S2 is longer than the normal spew S1 by 2 mm or more.

In the second method, the inner wall temperature of the vent hole 32 can be lowered by allowing air to flow through the vent hole 32 before starting vulcanization in the second vulcanization process. For example, air can be sent into the vent hole 32 from outside the mold 10 before starting vulcanization in the second vulcanization process. In other words, in the first vulcanization process, the operation of passing air through the vent holes 32 is not performed before starting vulcanization, and such an operation is performed only in the second vulcanization process. By such operation, the first vulcanization process and the second vulcanization process can be easily performed.

FIG. 5 shows changes in the temperature of the vent hole wall surface in the tire manufacturing method (second method) according to the present invention, FIG. 6 shows changes in the vulcanization degree of the rubber surface layer, and FIG. 7 shows changes in the spew length. is shown. 5 to 7, the horizontal axis represents the vulcanization time, and the vertical axes represent the temperature of the vent hole wall surface, the degree of vulcanization of the rubber surface layer, and the spew length, respectively. 5 to 7, solid lines indicate the first vulcanization process, and broken lines indicate the second vulcanization process.

As shown in FIG. 5, when the temperature of the wall surface of the vent hole is lowered by about 80° C. (broken line) before the start of vulcanization in the second vulcanization process (during the dry cycle), the temperature of the wall surface of the vent hole increases during vulcanization. It gradually increases as it progresses, and eventually matches the temperature (solid line) in the first vulcanization process. When the temperature of the vent hole wall surface is lowered by about 80° C. in this way, as shown in FIG. difference occurs. Specifically, in the second vulcanization process (dashed line), the time to reach the degree of stop-flow cure is delayed by about 5 seconds. As a result, as shown in FIG. 7, the second vulcanization process (dashed line) increases the spew length by about 2 mm. As is clear from FIGS. 5 to 7, when the temperature of the wall surface of the vent hole is reduced by at least 80° C. before vulcanization in the second vulcanization process starts, the spew length in the second vulcanization process increases by at least 2 mm. Become.

In the first and second methods described above, the frequency of the second vulcanization process may be 1/10 to 1/30 of the first vulcanization process. By performing the second vulcanization process at such a frequency, clogging of the vent holes 32 by the spew S1 can be effectively suppressed. If the frequency of the second vulcanization process is too low, the cleaning effect of the vent hole 32 will be insufficient. Dirt accumulates in the vicinity, which can cause clogging of the vent holes 32 .

A tire vulcanization mold having a molding surface for molding the outer surface of the tire and vent holes opening in the molding surface is used, and an unvulcanized pneumatic tire is put inside the tire vulcanization mold. Then, in repeatedly manufacturing a plurality of pneumatic tires by vulcanizing the pneumatic tire while pressurizing it toward the molding surface, part of the operation during vulcanization is changed to vulcanize the pneumatic tire. manufactured tires.

In the conventional example, a plurality of pneumatic tires were repeatedly manufactured under the same conditions. In Example 1, a first vulcanization process in which a pneumatic tire is vulcanized at a reference internal pressure at the initial stage of vulcanization, and a second vulcanization process in which a pneumatic tire is vulcanized at an internal pressure higher than the reference internal pressure at the initial stage of vulcanization. A vulcanization process was provided, and the frequency of the second vulcanization process was 1/10 of the frequency of the first vulcanization process. In Example 2, a first vulcanization process in which a pneumatic tire is vulcanized without manipulating the inner wall temperature of the vent hole before the start of vulcanization, and a state in which the inner wall temperature of the vent hole is lowered before the start of vulcanization A second vulcanization process for vulcanizing the pneumatic tire was provided, and the frequency of the second vulcanization process was 1/10 of the frequency of the first vulcanization process.

Vulcanization of the pneumatic tire was repeated by the methods of the conventional example and Examples 1 and 2, and the occurrence of clogging of the vent holes was investigated.

Regarding the occurrence of clogging of the vent holes, the number of times of vulcanization until clogging of the vent holes occurred was determined. In the evaluation results, the case where clogging occurred at 1000 times or less of vulcanization was indicated by "x", and the case where clogging occurred at 2000 times or less of vulcanization was indicated by "Δ". The case where clogging did not occur even after 2000 times was indicated by "○".

As can be seen from Table 1, in the methods of Examples 1 and 2, clogging of the vent hole due to spew could be effectively suppressed in comparison with the conventional example.

10 tire vulcanization mold 20 bladder 31 molding surface 32 vent hole T pneumatic tire S, S1, S2 Spew

Claims (6)

Using a tire vulcanization mold having a molding surface for molding the outer surface of the tire and a vent hole opening in the molding surface, putting an unvulcanized tire inside the tire vulcanization mold, In a method for repeatedly manufacturing a plurality of tires by vulcanizing the tire while pressurizing it against the molding surface,
A first vulcanization process for vulcanizing the tire at a reference internal pressure in the initial stage of vulcanization, and a second vulcanization process for vulcanizing the tire at an internal pressure higher than the reference internal pressure at the initial stage of vulcanization, A method of manufacturing a tire, characterized in that the second vulcanization process is performed at any frequency with respect to the first vulcanization process. When the tire is vulcanized, the inside of the tire is filled with a heating medium and then filled with a pressurized medium. 2. The method of manufacturing a tire according to claim 1, wherein the filling start timing of the pressurizing medium is set earlier than the filling start timing of the pressurizing medium. 3. The method of manufacturing a tire according to claim 1, wherein the frequency of said second vulcanization process with respect to said first vulcanization process is 1/10 to 1/30. Using a tire vulcanization mold having a molding surface for molding the outer surface of the tire and a vent hole opening in the molding surface, putting an unvulcanized tire inside the tire vulcanization mold, In a method for repeatedly manufacturing a plurality of tires by vulcanizing the tire while pressurizing it against the molding surface,
A first vulcanization process in which the tire is vulcanized without manipulating the inner wall temperature of the vent hole before the start of vulcanization; and a second vulcanization process for vulcanization, wherein the second vulcanization process is performed at any frequency with respect to the first vulcanization process. 5. The method of manufacturing a tire according to claim 4, wherein the inner wall temperature of the vent hole is lowered by allowing air to flow through the vent hole before starting vulcanization in the second vulcanizing process. The tire manufacturing method according to claim 4 or 5, wherein the frequency of said second vulcanization process with respect to said first vulcanization process is 1/10 to 1/30.

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