JP5701565B2 - Tire vulcanization bladder - Google Patents

Description

  The present invention relates to a tire vulcanizing bladder (hereinafter, also simply referred to as “blader”), and more specifically, the tire vulcanization is superior to conventional tires and can improve troubles such as pneumatic entry. Related to sulfur bladder.

  In general, in a tire manufacturing process, a tire molding bladder used when assembling each component of a tire to mold a raw tire (unvulcanized tire) and a final product tire shape at the time of vulcanization are provided. In general, two types of bladders are used, which are the tire vulcanizing bladder used in the above.

  In the production process of a pneumatic tire, particularly in the vulcanization process of an unvulcanized tire, as shown in FIG. 2, the green tire 5 (hereinafter also referred to as “tire”) in which a tire constituent member is usually incorporated is a mold. 6 and a rubber bag made of a cylindrical ring having a circular or horseshoe-shaped cross section called a bladder 11 is inserted into the inner cavity of the tire 5. Next, an internal pressure fluid such as steam or gas is introduced into the bladder 11, and the tire 5 is strongly pressed against the mold and simultaneously heated from the inside. At the same time, the tire 5 is vulcanized by heating from the outside by heating the mold with steam or the like.

  At this time, when the gauge of the bladder 11 is uniform, the bladder 11 swells in a round shape, so that the timing at which the bladder 11 contacts the side portion of the tire 5 is delayed, and as a result, the pressure of the tire 5 by the bladder 11 is weakened. There is a problem that defects such as air entry have occurred.

  Therefore, as a means for controlling the timing at which the bladder 11 contacts the side portion of the tire 5, for example, changing the gauge distribution of the bladder 11 can be considered. However, even if the gauge distribution of the bladder 11 is changed, the vulcanization degree distribution of the tire 5 is deteriorated and the vulcanization time is extended, and a new problem of adversely affecting the durability of the bladder 11 occurs. .

  Further, as another method for controlling the timing at which the bladder 11 contacts the side portion of the tire 5, the bladder circumferential length of the portion contacting the tread center portion of the tire 5, as in the bladder described in Patent Document 1, is used. It is also conceivable that the length of the bladder is shorter than the circumference of the portion in contact with the shoulder portion so that the portion in contact with the tread center is locally recessed.

Japanese Patent Laid-Open No. 2005-1111889

  However, as in the case of the bladder described in Patent Document 1, if the portion in contact with the tread center is locally recessed, air may be enclosed between the tire and the bladder, resulting in a defective tire. high. As described above, it is difficult to improve the moldability of the tire without causing problems such as air entry, and it is currently desired to develop a new technology.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a tire vulcanizing bladder that is more excellent in tire formability than conventional ones and that can improve problems such as air entry.

  As a result of intensive studies to solve the above problems, the present inventor has found that the above-mentioned problems can be solved by setting a portion that contacts the tread center portion of the bladder to a predetermined structure, thereby completing the present invention. It came to.

That is, the tire vulcanization bladder of the present invention is a tire vulcanization bladder in which the tire is sandwiched between a mold and inflated to press the tire against the mold.
When the tire vulcanization bladder has a recess in the portion that abuts the tread center portion, and the length of the tire vulcanization bladder in the width direction of the bladder is W, the length Wa of the recess in the width direction of the bladder Is 0.6 W to 0.9 W,
The concave portion is inclined toward the center portion in the bladder width direction, has a flat bottom portion at the center portion, and the length Wb in the bladder width direction of the bottom portion is 0.2 W to 0.5 W. It is characterized by.

In the tire vulcanizing bladder according to the present invention, when the maximum circumferential length of the tire vulcanizing bladder is L, the length of the bladder circumferential length Lc in contact with the tread center portion is 0.8L or more and less than 1.0L. It is preferable that Furthermore, it is preferable that a distance Wc from the tread center portion to a portion that becomes the maximum circumferential length L of the tire vulcanizing bladder is 0.3 W or more.

  According to the present invention, the above configuration can provide a tire vulcanization bladder that is more excellent in tire formability than conventional and can improve problems such as air entry.

It is explanatory drawing of an example of the bladder for tire vulcanization | cure of this invention. It is explanatory drawing of the vulcanization process of an unvulcanized tire.

Hereinafter, preferred embodiments of the present invention will be described in detail.
FIG. 1 is an explanatory view of an example of a tire vulcanizing bladder according to the present invention. The bladder 1 of the present invention is configured such that a tire is sandwiched between molds, a high-temperature / high-pressure vulcanizing medium is supplied into the bladder 1 and expanded to press the tire against the mold. As shown in FIG. 1, the bladder 1 of the present invention has a width Wa of 0.6 W to 0. It has a recess 2 that is 9W. Thereby, when the bladder 1 is expanded, the bladder 1 comes into contact with the tire from the shoulder portion, the vulcanization speed and the pressure can be made uniform, and appropriate vulcanization can be performed.

  That is, by providing the concave portion 2 at a portion that contacts the tread center portion of the bladder 1, the timing at which the bladder 1 contacts the tread center portion is delayed, while the timing at which the bladder 1 contacts the tire side portion relatively earlier. And press can be improved. Thereby, it can prevent that the vulcanization | cure from a tread center part advances excessively.

  Further, the recess 2 forms a space for air to escape between the tire inner surface and the bladder 1 so that the air is not wrapped. As a result, it is possible to suppress poor air entry into the tire. In order to obtain such an effect satisfactorily, the width Wa of the recess 2 in the width direction is preferably 0.7 W to 0.8 W.

  Here, the tread center portion refers to a surface portion located at the center of the outer peripheral surface where the groove of the tire is formed. Moreover, the part which contact | abuts the tread center part of the bladder 1 means the outer peripheral surface part of the bladder which contact | abuts the above-mentioned tread center part, when it expand | swells in the bladder 1 and is used for vulcanization molding.

  Further, the shoulder portion refers to a sloped region portion that exists between the above-described tread center portion and sidewall portion of the tire, and the portion that contacts the shoulder portion of the bladder 1 is expanded and vulcanized in the bladder. The outer peripheral surface portion of the bladder that comes into contact with the above-described tread shoulder portion when being used for molding.

  In the present invention, the recess 2 is inclined toward the center in the bladder width direction, has a flat bottom 3 at the center of the recess 2, and the length Wb of the bottom 3 in the bladder width direction is 0.2 W. It is preferable that it is -0.5W. By providing the inclination applied to the recess 2, air can be pushed out well when the bladder 1 is expanded. Thereby, troubles, such as air entering, can be improved favorably. In addition, by setting the length Wb of the bottom portion 3 in the bladder width direction within the above range, it is possible to maintain a good balance between the extrusion of air and the pressure of the bladder 1.

  In the present invention, when the maximum circumferential length of the bladder 1 is L, it is preferable that the length of the bladder circumferential length Lc at the portion in contact with the tread center portion is 0.8L or more and less than 1.0L. If the length of the bladder circumferential length Lc in contact with the tread center portion is less than 0.8 L, the timing at which the bladder 1 contacts the tread center portion becomes too late, and the vulcanization speed and the pressing force can be made uniform. This is because there are cases where it is not possible.

  Furthermore, in the present invention, the distance Wc from the tread center portion to the portion (the bladder maximum peripheral length portion 4) that becomes the maximum peripheral length L of the bladder 1 is preferably 0.3 W or more. When the distance from the tread center to the bladder maximum circumferential length portion 4 is 0.3 W or more, that is, the bladder maximum circumferential length portion 4 is provided in the shoulder portion, the tire can be uniformly vulcanized.

  In the present invention, the gauge thickness of the bladder 1 is preferably 3.0 to 5.0 mm at the thinnest part from the viewpoints of manufacturability, durability and shape maintenance.

  In the present invention, with respect to the structure of the bladder, there is a recess in the portion that comes into contact with the tread center portion of the tire vulcanization bladder, and when the length in the width direction of the bladder of the tire vulcanization bladder is W, The length Wa in the width direction of the bladder may be 0.6 W to 0.9 W, and thereby the desired effect of the present invention can be obtained, and for other specific blending contents such as a bladder rubber compound, etc. There is no particular limitation. For example, as the bladder rubber, butyl rubber having excellent corrosion resistance and high air impermeability can be used.

  Hereinafter, the present invention will be described more specifically with reference to examples. The present invention is not limited by the following description.

<Example>
A bladder having an outer contour shape shown in FIG. 1 corresponding to a tire having a tire size of 245 / 35R19 was produced. The width Wa of the recess is 0.75 W, the width Wb of the bottom is 0.38 W, the bladder circumferential length Lc of the portion in contact with the tread center portion is 0.93 L, and the distance Wc from the tread center portion to the longest bladder circumferential length is 0.375W. Using the obtained bladder, 1000 tires were vulcanized, and the defect occurrence rate due to air entering the tires was investigated.

<Comparative example>
A bladder of a conventional shape corresponding to a tire having a tire size of 245 / 35R19 and having no recess in the portion in contact with the tread center portion of the type shown in FIG. 2 was produced. Using the obtained bladder, 500 tires were vulcanized, and similarly, the occurrence rate of defects due to entering of tire air was investigated.

<Result>
As a result of the above investigation, by using the bladder of the present invention, it was possible to reduce the occurrence rate of in-tire incomplete tires by 80% compared to the case of using the conventional bladder. Moreover, the pressing of the tread center portion and the tire side portion was improved, and uniform vulcanization was achieved. As a result, it was found that the bladder of the present invention has better tire moldability than conventional ones and can improve problems such as air entry.

1,11 Bladder 2 Recess 3 Bottom 4 Maximum circumference of bladder 5 Tire 6 Mold

Claims (3)

In a tire vulcanization bladder that presses the tire against the mold by sandwiching the tire between the mold and inflating,
When the tire vulcanization bladder has a recess in the portion that abuts the tread center portion, and the length of the tire vulcanization bladder in the width direction of the bladder is W, the length Wa of the recess in the width direction of the bladder There Ri 0.6W~0.9W der,
The concave portion is inclined toward the center portion in the bladder width direction, has a flat bottom portion at the center portion, and the length Wb in the bladder width direction of the bottom portion is 0.2 W to 0.5 W. Tire vulcanizing bladder. When the maximum circumference of the tire vulcanizing bladder is L, the tire vulcanization according to claim 1, wherein the length of the bladder circumference Lc of the portion contacting the tread center portion is less than or 0.8 L 1.0 L For bladder. The tire vulcanization bladder according to claim 1 or 2 , wherein a distance Wc from the tread center portion to a portion having the maximum circumferential length L of the tire vulcanization bladder is 0.3 W or more.

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