JP2005271534A - Vulcanizing method of pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vulcanizing method of a pneumatic tire enabling the acquirement of good grip without greatly extending a vulcanization time by optimizing a vulcanization degree of an outer surface of a tread portion. <P>SOLUTION: In the vulcanizing method of the pneumatic tire heating a non-vulcanized tire with an internal heating means arranged inside of the tire and an external heating means arranged outside of the tire at the same time, the outer surface of the tread portion is subjected to the latest vulcanization based on the heating conditions of the internal heating means and the external heating means, and equivalent vulcanization degrees satisfy 1.1≤B/A≤1.6 and 1.7≤C/A≤4.5 wherein A, B and C are equivalent vulcanization degrees of the outer surface at the maximum gauge position of the tread portion, the center in the thickness direction and the inner surface respectively. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a vulcanization method for a pneumatic tire in which an unvulcanized tire is simultaneously heated by an internal heating means disposed inside the tire and an external heating means disposed outside the tire, and more specifically, a vulcanization time. The present invention relates to a method for vulcanizing a pneumatic tire that optimizes the degree of vulcanization of the outer surface of the tread portion without significantly extending the tire width and makes it possible to obtain good grip characteristics.

  As a method of vulcanizing a pneumatic tire, an unvulcanized tire is simultaneously heated by an internal heating means (for example, steam) disposed on the inner side of the tire and an external heating means (for example, a heater) disposed on the outer side of the tire. It is generally done. In such a vulcanizing method, the heating conditions of the internal heating means and the external heating means are controlled in consideration of the vulcanization degree distribution inside the tire (for example, see Patent Document 1).

However, in the above vulcanization method, the internal temperature and external temperature are set to a relatively high temperature in order to sufficiently vulcanize the inside of the tire. As a result, the outer surface of the tread portion is overvulcanized, resulting in good grip. There is a problem that characteristics cannot be obtained. In particular, when the vulcanization temperature is increased in order to increase the productivity of a pneumatic tire, the grip characteristics are significantly deteriorated. On the other hand, when the vulcanization temperature is lowered in order to reduce the overvulcanization of the tread portion, the vulcanization time is greatly extended.
JP-A 63-17010

  An object of the present invention is to provide a method for vulcanizing a pneumatic tire that can optimize the degree of vulcanization of the outer surface of the tread portion without significantly extending the vulcanization time and obtain good grip characteristics. There is.

  The method for vulcanizing a pneumatic tire according to the present invention for solving the above-described object is the air for simultaneously heating an unvulcanized tire by means of an internal heating means disposed inside the tire and an external heating means disposed outside the tire. In the vulcanizing method of the tire, the outer surface of the tread portion is the latest vulcanization based on the heating conditions by the internal heating means and the external heating means, and the outer surface at the maximum gauge position of the tread portion, the central portion in the thickness direction When the equivalent vulcanization degree at the end of vulcanization on the inner surface is A, B, C, respectively, these equivalent vulcanization degrees are 1.1 ≦ B / A ≦ 1.6 and 1.7 ≦ C / A Vulcanization is performed so as to satisfy the relationship of ≦ 4.5.

  In the present invention, the heating temperature by the external heating means is relatively lowered with respect to the heating temperature by the internal heating means to make the outer surface of the tread part the latest vulcanization, and the thickness direction at the maximum gauge position of the tread part By defining the equivalent vulcanization degree of each part as described above, it is possible to optimize the vulcanization degree of the outer surface of the tread portion without significantly extending the vulcanization time and to ensure good grip characteristics. . Further, when the heating temperature by the internal heating means is further lowered so that the equivalent vulcanization degree relationship is 1.1 ≦ B / A ≦ 1.3 and 1.7 ≦ C / A ≦ 2.5, the tread portion The optimum vulcanization range is expanded to the inside, and even better grip characteristics can be obtained.

In the present invention, the equivalent degree of vulcanization means that the actual vulcanization temperature is T (° C.), the vulcanization time at the vulcanization temperature T is t (minutes), and an arbitrary reference temperature is T ₀ (° C.). When the vulcanization time at the reference temperature T ₀ is t ₀ (min), the integrated value of the vulcanization time t ₀ converted from the vulcanization reaction rate equation of the following equation (1).
t ₀ = t × α ^{(T-T0) / 10} (1)
Where α is a vulcanization temperature coefficient (ratio of vulcanization rates when the temperature changes by 10 ° C.).

In the present invention, the vulcanization time from the start of heating to the vulcanized state that exhibits 95% of the maximum torque by heating at the reference temperature T ₀ is defined as t ₉₅ (minutes), and the addition of ₉₅ to 100% of the maximum torque is performed. When the maximum vulcanization time for maintaining the vulcanized state is t _max (minutes), the equivalent vulcanization degree A on the outer surface of the tread portion is preferably in the range of t ₉₅ ≦ A ≦ t _max . Thereby, a grip characteristic can be made into the most favorable state.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.

  The pneumatic tire vulcanization method of the present invention is a pneumatic tire vulcanization method in which an unvulcanized tire is simultaneously heated by an internal heating means disposed inside the tire and an external heating means disposed outside the tire. is there. The specific configuration of the vulcanizing apparatus is not particularly limited, but it is necessary that at least an internal heating means and an external heating means are provided and the heating conditions of these heating means can be controlled independently.

  1 to 4 show the relationship between the position of the tread portion in the thickness direction and the degree of vulcanization. FIG. 1 shows the case where heating is performed only with the internal heating means, and FIG. 2 shows the case where heating is performed only with the external heating means. FIG. 3 shows a case where heating is performed by a conventional method using an internal heating means and an external heating means, and FIG. 4 shows a case where heating is performed by the method of the present invention using an internal heating means and an external heating means. It is.

  As shown in FIG. 1, when heating is performed only with the internal heating means, the degree of vulcanization on the inner surface of the tread is satisfied, but the degree of vulcanization on the outer surface of the tread becomes insufficient. As shown in FIG. 2, when heating is performed only with the external heating means, the degree of vulcanization on the inner surface of the tread is insufficient, while the degree of vulcanization on the outer surface of the tread is satisfied. On the other hand, as shown in FIG. 3, when heating is performed using both the internal heating means and the external heating means, the vulcanization degree of the outer surface of the tread and the inner surface of the tread tends to be excessive. In FIG. 3, curve X is a high temperature setting, curve Y is a normal temperature setting, and curve Z is a low temperature setting.

  On the other hand, in the present invention, as shown in FIG. 4, based on the heating conditions by the internal heating means and the external heating means, the vulcanization is performed so that the vulcanization degree of the outer surface of the tread becomes the lowest at the end of vulcanization. It controls the progress.

  FIG. 5 shows an example of a pneumatic tire vulcanized in the present invention. In FIG. 5, 1 is a tread portion, 2 is a sidewall portion, and 3 is a bead portion. The tread portion 1 has the largest gauge in the shoulder region, and it is important to optimize the vulcanization state of the portion. Here, at a position where the gauge of the tread portion 1 measured along the normal line of the inner surface of the tread portion 1 is maximized (maximum gauge position), a point where the normal line and the outer surface of the tread intersect is a. Let c be the point where the normal line and the inner surface of the tread intersect, and let b be the center point (the center in the thickness direction) between point a and point c. When the equivalent vulcanization degrees at the end of vulcanization at points a, b and c are A, B and C, respectively, these equivalent vulcanization degrees are 1.1 ≦ B / A ≦ 1.6 and 1. 7 ≦ C / A ≦ 4.5, more preferably, vulcanization is performed so as to satisfy the relationship of 1.1 ≦ B / A ≦ 1.3 and 1.7 ≦ C / A ≦ 2.5. To do.

  Thereby, the degree of vulcanization of the outer surface of the tread can be optimized without significantly extending the vulcanization time, and good grip characteristics can be ensured. Here, if the ratio B / A of the equivalent vulcanization degree is less than 1.1, the effect of improving the grip characteristics becomes insufficient. Conversely, if it exceeds 1.6, the flatness of the vulcanization degree inside the tread deteriorates. As a result, the vulcanization time becomes longer as well as a decrease in driving performance. Further, if the ratio C / A of the equivalent vulcanization degree is less than 1.7, the effect of improving the grip characteristics becomes insufficient. Conversely, if it exceeds 4.5, the flatness of the vulcanization degree inside the tread deteriorates. As a result, the vulcanization time becomes longer as well as a decrease in running performance.

The above-mentioned equivalent vulcanization degree is defined by taking the actual vulcanization temperature as T (° C.), the vulcanization time at the vulcanization temperature T as t (min), and any reference temperature as T ₀ (° C.). When the vulcanization time at the temperature T ₀ is t ₀ (minutes), this is an integrated value of the vulcanization time t ₀ converted from the following vulcanization reaction rate equation based on the Van't Hoff law.

t ₀ = t × α ^{(T-T0) / 10}
Where α is a vulcanization temperature coefficient (ratio of vulcanization rates when the temperature changes by 10 ° C.). The vulcanization temperature coefficient α is an arbitrary constant that varies in the range of 1.8 to 2.5 depending on the type and amount of raw rubber, vulcanization system, filler, etc., but α = 2 may be used as a simple method. . What is necessary is just to measure with a rheometer etc., when employ | adopting an exact value as vulcanization temperature coefficient (alpha). On the other hand, 150 ° C. may be selected as the reference temperature T ₀ in normal rubber vulcanization.

Here, Table 1 shows a calculation example for obtaining the equivalent vulcanization degree at the end of vulcanization when T ₀ = 150 ° C. and α = 2. The vulcanization temperature T and the vulcanization time t described in Table 1 are data relating to the outer surface of the tread at the maximum gauge position.

As shown in Table 1, when the actual vulcanization temperature T is changed by 5 ° C. every minute from 125 ° C. to 170 ° C., the equivalent vulcanization degree consisting of the integrated value of the converted vulcanization time t _0. Is 13.23 minutes. In other words, according to the above heating schedule, the vulcanized state is equivalent to the case where heating is performed at the reference temperature T ₀ (150 ° C.) for 13.23 minutes.

In the present invention, it is necessary to specify the ratio of the equivalent vulcanization degree A to C of each part at the maximum gauge position of the tread part, but the equivalent vulcanization degree A on the outer surface of the tread part is optimized. It is also important to do. Therefore, the vulcanization time from ₉₅ to 100% of the maximum torque is defined as t ₉₅ (minutes) from the start of heating to the vulcanized state that exhibits 95% of the maximum torque by heating at the reference temperature T _0. When the maximum vulcanization time for maintaining the pressure is t _max (min), the equivalent vulcanization degree A on the outer surface of the tread portion is preferably in the range of t ₉₅ ≦ A ≦ t _max .

FIG. 6 illustrates the relationship between the vulcanization time and torque of the rubber composition. That is, FIG. 6 shows a change in torque (N · m) when a rubber composition to be measured for the equivalent vulcanization degree A is vulcanized at a reference temperature T ₀ (150 ° C.) using a rheometer. . As shown in FIG. 6, as the vulcanization progresses, the torque of the rubber composition increases, reaching a vulcanized state that exhibits 95% of the maximum torque at the vulcanization time t ₉₅ (min), and the maximum vulcanization time t Maintain a vulcanized state exhibiting 95-100% of maximum torque until _max (min). That is, since the vulcanized state exhibiting 95 to 100% of the maximum torque is the most preferable state, the equivalent vulcanization degree A on the outer surface of the tread portion is set to the range of t ₉₅ ≦ A ≦ t _max. Grip characteristics can be obtained.

When vulcanizing a pneumatic tire having a tire size of 195 / 55R15, the heating conditions were varied as shown in Table 2 (conventional examples, comparative examples 1 to 3 and examples 1 to 3). And about the obtained tire, the driving | running | working test in the circuit was implemented and the lap time was measured. The evaluation results are shown as an index with the conventional example being 100. The smaller the index value, the better the grip characteristics of the tread portion and the better the steering stability.

  As shown in Table 2, in Comparative Example 1, the external temperature was set higher than that in the conventional example, so that the tread portion was overvulcanized and the running performance was deteriorated. On the other hand, in Examples 1 to 3, the external temperature was set lower than the conventional example, and as a result, the equivalent vulcanization degree of each part of the tread portion was 1.1 ≦ B / A ≦ 1.6 and 1 Since the relationship of 7 ≦ C / A ≦ 4.5 was satisfied, the vulcanized state of the tread portion was optimized, and excellent running performance could be exhibited. In particular, in Example 3, the internal temperature was also set lower than in the conventional example, and the equivalent vulcanization degree of each part of the tread portion was 1.1 ≦ B / A ≦ 1.3 and 1.7 ≦ C / A ≦ 2. Since the relationship of .5 was satisfied, the best grip characteristics could be obtained.

  In Comparative Example 2, the external temperature was set lower than in Examples 1 to 3, and as a result, the ratio B / A and the ratio C / A of the equivalent vulcanization degree of each part of the tread portion were out of the predetermined range. For this reason, the flatness of the vulcanization degree inside the tread is deteriorated, the effect of improving the running performance becomes insufficient, and the vulcanization time is extended.

  In Comparative Example 3, the internal temperature is set lower than that of Comparative Example 2 and attempts are made to improve the flatness of the vulcanization degree inside the tread. However, the improvement effect is insufficient, and the vulcanization time is further reduced. It was extended.

It is a graph which shows the relationship between the position of the thickness direction of a tread part at the time of heating only with an internal heating means, and a vulcanization degree. It is a graph which shows the relationship between the position of the thickness direction of a tread part at the time of heating only with an external heating means, and a vulcanization degree. It is a graph which shows the relationship between the position of the thickness direction of a tread part, and a vulcanization degree at the time of heating by a conventional method using an internal heating means and an external heating means. It is a graph which shows the relationship between the position of the thickness direction of a tread part at the time of heating by the method of this invention using an internal heating means and an external heating means, and a vulcanization degree. It is a meridian half section view showing an example of a pneumatic tire vulcanized by the method of the present invention. It is a graph which illustrates the relationship between the vulcanization time of a rubber composition, and torque.

Explanation of symbols

1 Tread part 2 Side wall part 3 Bead part a point (tread outer surface)
Point b (thickness direction center)
Point c (tread inner surface)

Claims (4)

In a vulcanizing method for a pneumatic tire in which an unvulcanized tire is simultaneously heated by an internal heating means arranged on the inner side of the tire and an external heating means arranged on the outer side of the tire, heating conditions by the internal heating means and the external heating means The outer surface of the tread portion is defined as the latest vulcanization based on the above, and the equivalent vulcanization degree at the end of vulcanization at the outer surface, the central portion in the thickness direction, and the inner surface at the maximum gauge position of the tread portion is A and B, respectively. , C, the equivalent vulcanization degree is 1.1 ≦ B / A ≦ 1.6 and 1.7 ≦ C / A ≦ 4.5. Vulcanization method. The pneumatic tire according to claim 1, wherein vulcanization is performed so that the equivalent degree of vulcanization satisfies a relationship of 1.1≤B / A≤1.3 and 1.7≤C / A≤2.5. Vulcanization method. The equivalent vulcanization degree is defined by taking the actual vulcanization temperature as T (° C.), the vulcanization time at the vulcanization temperature T as t (minutes), and any reference temperature as T ₀ (° C.). The integrated value of the vulcanization time t ₀ converted from the vulcanization reaction rate equation of the following formula (1), where vulcanization time at the temperature T ₀ is t ₀ (min). A method for vulcanizing a pneumatic tire as described in 1.
t ₀ = t × α ^{(T-T0) / 10} (1)
Where α is a vulcanization temperature coefficient (ratio of vulcanization rates when the temperature changes by 10 ° C.). The vulcanization time from ₉₅ to 100% of the maximum torque is defined as the vulcanization time from the start of heating to the vulcanized state that exhibits 95% of the maximum torque by heating at the reference temperature T _0, where t ₉₅ (min). The pneumatic tire according to claim 3, wherein the equivalent vulcanization degree A on the outer surface of the tread portion is in the range of t ₉₅ ≦ A ≦ t _max when the maximum vulcanization time to be maintained is t _max (min). Vulcanization method.

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