JP2013184391A - Tire vulcanizing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tire vulcanizing method capable of sufficiently preventing the generation of porosity without prolonging a vulcanization time and improving production capability in vulcanization.SOLUTION: A tire vulcanizing method supplies a heating and pressurizing medium into the inside of a tire mounted in a vulcanization mold and vulcanizes the tire. A discharging step of discharging the heating and pressurizing medium supplied into the tire after predetermined heating and pressurizing performs the discharge for 50-120 s at an average pressure reduction rate of 0.012 to 0.044 MPa/s until the pressure in the tire becomes the atmospheric pressure, wherein a pressure reduction state accompanying the discharge is divided into 5 to 10 stages, and a pressure reduction ratio per stage after performing 70-80% of the discharge is adjusted to 1.5-3.0 times the pressure reduction ratio per stage before the 70-80% of the discharge.

Description

  The present invention relates to a tire vulcanization method capable of suppressing the generation of porosity (bubbles) inside a tire without lengthening the vulcanization time.

  In general, a tire is vulcanized by mounting a non-vulcanized tire and a bladder in a vulcanization mold, and then supplying a heating / pressurizing medium such as steam into the tire and heating / pressurizing the tire. After the vulcanization is completed, the heating / pressurizing medium is discharged from the inside of the tire to reduce the pressure in the tire to atmospheric pressure, and then the product tire is taken out from the vulcanization mold.

  However, in the conventional vulcanization, in the exhaust process, the pressure in the tire is abruptly reduced, for example, to 10 atmospheric pressure in a short time of 10 to 20 seconds (decompression). Porosity tends to occur in the tire during vulcanization, which may cause product defects. In addition, since a sudden pressure change gives a large load to the bladder, there is a risk of reducing the bladder life.

  In order to suppress the generation of this porosity, conventionally, the heating / pressurization time has been lengthened, but as a result, the vulcanization time is lengthened and the vulcanization production capacity is reduced. There was a problem.

  In view of this, the present applicant firstly reduced the pressure in the tire to a predetermined pressure in the vulcanization method using a heating / pressurizing medium, and heated when the predetermined pressure was reached. A vulcanization method for discharging the pressurized medium was proposed (Patent Document 1).

Japanese Patent Laid-Open No. 11-77704

  In view of the above, the present invention provides a tire vulcanization method that can sufficiently suppress the generation of porosity without increasing the vulcanization time and can further improve the vulcanization production capacity. Is an issue.

The invention described in claim 1
A tire vulcanization method for vulcanizing the tire by supplying a heating / pressurizing medium into a tire mounted in a vulcanization mold,
An exhaust process for exhausting the heating / pressurizing medium supplied into the tire after predetermined heating and pressurization,
Exhaust in 50 to 120 seconds at an average pressure reduction rate of 0.012 to 0.044 MPa / second until the pressure in the tire reaches atmospheric pressure,
The decompressed state accompanying the exhaust is divided into 5 to 10 stages,
It is an exhaust process in which the decompression rate per stage after exhausting 70 to 80% is 1.5 to 3.0 times the decompression rate per stage up to the exhaust of 70 to 80%. This is a tire vulcanizing method.

  ADVANTAGE OF THE INVENTION According to this invention, the generation | occurrence | production of a porosity can fully be suppressed without extending vulcanization time, and the tire vulcanization method which can improve the production capacity of vulcanization can be provided.

It is a figure which shows the relationship between the vulcanization time in the vulcanization method of the tire of one embodiment of this invention, and the pressure in a tire.

  Hereinafter, an embodiment of a tire vulcanizing method according to the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing the relationship between the vulcanization time and the pressure in the tire in the tire vulcanization method of the present embodiment. In FIG. 1, the horizontal axis indicates the vulcanization time, that is, the elapsed time (seconds) after the start of vulcanization, and the vertical axis indicates the pressure in the tire disposed in the vulcanizer.

  The vulcanization of the tire according to the present embodiment is performed according to the pressure curve 10 shown in FIG. 1, and proceeds in the order of the heating / pressurizing medium supply process, the heating / pressurization process, and the exhaust process. These steps correspond to A, B, and C shown in FIG. FIG. 1 also shows a pressure curve 20 in conventional vulcanization.

  Specifically, as in the conventional vulcanization of tires, first, an unvulcanized tire is mounted in a vulcanization mold, and then a bladder is mounted in the unvulcanized tire. Next, the vulcanization mold is closed, and a heating / pressurizing medium is supplied into the bladder until the tire internal pressure reaches a predetermined pressure. As a result, the bladder expands and presses the unvulcanized tire against the inner surface of the mold (heating / pressurizing medium supplying step).

  Next, heating and pressurizing are performed for a predetermined time while maintaining the tire internal pressure at a predetermined pressure. Thereby, the vulcanization of the unvulcanized tire proceeds (heating / pressurizing step).

  Next, the heating / pressurizing medium in the bladder is exhausted to the outside, the tire internal pressure is reduced to atmospheric pressure, and the vulcanized tire is taken out from the vulcanization mold (exhaust process).

  In this embodiment, the exhaust for reducing the tire internal pressure to atmospheric pressure is not a short time of 10 to 20 seconds as in the prior art, but at a slow average pressure reduction rate of 0.012 to 0.044 MPa / second, It takes 50 to 120 seconds. Here, the “average pressure reduction speed” refers to the average pressure reduction speed of the tire internal pressure from the tire internal pressure at the start of exhaust (decompression start pressure) to the tire internal pressure at the time of exhaust completion (decompression end pressure).

  In addition, this exhaust is not exhausted to atmospheric pressure at a time, but is exhausted in 5 to 10 stages of decompression. Further, the decompression rate at each stage is not uniform, and the decompression rate per stage after exhausting 70 to 80% is 1 of the decompression rate per stage up to 70 to 80% exhaust. Set to 5 to 3.0 times. FIG. 1 shows a state where exhaust is performed in 10 stages of 10a to 10j.

  In this way, by taking a long time of 50 to 120 seconds and further reducing the pressure in steps and exhausting it, the generation of porosity can be sufficiently suppressed by increasing the decompression rate at that time in the latter half. .

  That is, the minute air contained in the tire rubber is heated and pressurized at a high temperature during vulcanization, so the pressure is high, and the tire rubber itself is soft at a high temperature, so the tire internal pressure is large. When returning to atmospheric pressure, the rubber loses the pressure of the minute air and the minute air tends to become porosity on the tire surface. At this time, if this pressure reduction is performed at once, a large pressure gradient is instantaneously generated in the thickness direction of the rubber, and the inner bubbles gather on the surface side.

  However, in the present embodiment, as described above, exhaust is performed step by step while adjusting the decompression rate at a slow decompression speed, so that a large pressure gradient does not occur in the exhaust, and the rubber The pressure is kept uniform in the thickness direction, the state during vulcanization is kept, and the generation of porosity can be sufficiently suppressed.

  On the other hand, conventionally, as shown in the pressure curve 20 shown by a thick broken line in FIG. 1, after heating and pressurizing time is extended, vulcanization is carried out overly and fine air is enclosed in rubber, A vacuum was applied. As a result, the generation of porosity due to rapid exhaust of 10 to 20 seconds could be suppressed, but as shown in FIG. 1, the entire vulcanization process time (vulcanization time) was increased, and vulcanization was performed. The production capacity has been reduced.

  However, in the present embodiment, the heating / pressurizing time is not extended, and after reaching the predetermined vulcanized state, the pressure reduction is started at an early stage and the exhaust is slowly performed. Although the time of the exhaust process is longer than before, the time of the entire vulcanization process (vulcanization time) can be made shorter than before as shown in FIG. 1 to improve the production capacity of vulcanization. Can do.

  Furthermore, in the present embodiment, a rapid pressure change in the tire is suppressed and the load on the vulcanizing bladder is reduced, so that the life of the vulcanizing bladder can be extended.

  Note that the present invention can be applied even if the tire size, the exhaust capacity of the vulcanizer, and the like are changed, and the above-described effects are similarly exhibited.

  In the following examples and comparative examples, tires having a tire size of 195 / 65R15 DSX-2 were produced and evaluated.

  Specifically, an unvulcanized tire was mounted in a vulcanization mold corresponding to the tire of the above size, and then a bladder was mounted in the unvulcanized tire. Next, the vulcanization mold was closed, and a heating / pressurizing medium (nitrogen gas) was supplied into the bladder until the tire internal pressure reached 2.2 MPa. Next, heating and pressurization were performed for 8.5 minutes while maintaining the tire internal pressure.

  Next, the heating / pressurizing medium in the bladder is exhausted to the outside according to the exhausting process shown in Table 1, and after reducing the tire internal pressure to atmospheric pressure, the vulcanized tire is taken out from the vulcanization mold, A product tire was made. In addition, four product tires were produced for each example.

  In Comparative Examples 1 and 2, the heating time was extended by 1.0 minute as in the prior art.

  About each produced tire, while evaluating the vulcanization time, the bubble generation frequency, and the generation | occurrence | production state of the vulcanized tire scrap, it evaluated the bladder life. In addition, evaluation in each item was performed by an index with the result in Comparative Example 2 (exhaust time 20 seconds) as a conventional example being 100. The results are shown in Table 1.

  From Table 1, when the exhaust time is 50 to 120 seconds, the average pressure reduction rate is 0.012 to 0.044 MPa / second, and exhaust is performed in 5 to 10 stages (Example 1 to Example 6), conventional Compared with (Comparative Example 2), it was confirmed that the vulcanization time was shortened by a maximum of 6%, the bubble generation frequency was decreased by a maximum of 6%, and the generation of vulcanized tire scrap was decreased by a maximum of 4%. It was also confirmed that the bladder life was increased by up to 9%.

  Such an effect is obtained by reducing the decompression rate per step after exhausting 70 to 80% in stepwise exhaust to 1 of the decompression rate per step until exhausting 70 to 80%. The present inventors have confirmed that it can be obtained by setting the ratio to 5 to 3.0 times.

  On the other hand, when the exhaust time was 10 seconds (Comparative Example 1), it was confirmed that the shortening of the vulcanization time was not observed and the improvement of the production capacity could not be expected. In addition, an increase in the occurrence frequency of bubbles by 6% and an increase in generation of vulcanized tire scraps by 16% were observed, confirming that the tire quality was generally deteriorated. Furthermore, it was confirmed that the bladder life was also reduced by 14%.

  When the exhaust time was 30 seconds (Comparative Example 3) and 40 seconds (Comparative Example 4), it was confirmed that the vulcanization time was not shortened and the production capacity could not be improved. In addition, it was confirmed that the generation frequency of bubbles and generation of vulcanized tire scrap could not be sufficiently reduced, and improvement in tire quality could not be expected. Furthermore, it was confirmed that the bladder life was not sufficiently extended.

  Further, when the exhaust time is 140 to 180 seconds (Comparative Examples 5 to 7), the bladder life is increased, but the vulcanization time is longer than that of Comparative Example 2, and an improvement in production capacity can be expected. It was confirmed that there was no. It was also confirmed that the bubble generation frequency and the generation of vulcanized tire scrap were inferior to those of the Examples, and were almost the same as in the past. In the case of Comparative Examples 5 to 7, the applicable size is limited.

  While the present invention has been described based on the embodiments, the present invention is not limited to the above embodiments. Various modifications can be made to the above-described embodiments within the same and equivalent scope as the present invention.

DESCRIPTION OF SYMBOLS 10 Pressure curve 10a-10j Each stage of pressure reduction 20 Pressure curve in the conventional vulcanization method A Heating / pressurizing medium supply process B Heating / pressurizing process C Exhaust process

Claims (1)

A tire vulcanization method for vulcanizing the tire by supplying a heating / pressurizing medium into a tire mounted in a vulcanization mold,
An exhaust process for exhausting the heating / pressurizing medium supplied into the tire after predetermined heating and pressurization,
Exhaust in 50 to 120 seconds at an average pressure reduction rate of 0.012 to 0.044 MPa / second until the pressure in the tire reaches atmospheric pressure,
The decompressed state accompanying the exhaust is divided into 5 to 10 stages,
It is an exhaust process in which the decompression rate per stage after exhausting 70 to 80% is 1.5 to 3.0 times the decompression rate per stage up to the exhaust of 70 to 80%. A tire vulcanizing method.

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