JPH07195380A - Tire vulcanizing bladder and method - Google Patents

Abstract

PURPOSE:To achieve the extension of the life and the reduction of the production cost of a tire vulcanizing bladder, the prevention of the crack of the inner surface of a tire and the reduction of the use amt. of a release agent in a vulcanizing process. CONSTITUTION:Fine unevenness 26 for escaping air between a bladder and the inner surface of a tire is formed on the outer peripheral surface of the bladder 10. Since the fine unevenness can be obtained by applying shot blasting low in processing cost to the mold vulcanizing the bladder 10, the production cost of the bladder 10 is reduced. Since the outer peripheral surface of the bladder 10 has fine unevenness, a region where stress is conc. is eliminated and a crack is hard to generate and life is extended. Since the inner surface of the tire also becomes a fine uneven state, the crack of the inner surface of the tire is hard to generate at the time of the running of the tire.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tire vulcanization bladder used for vulcanizing a pneumatic tire and a tire vulcanizing method.

[0002]

2. Description of the Related Art In a tire vulcanizing apparatus for vulcanizing a pneumatic tire, a bladder for tire vulcanization, which is made of an elastic material such as rubber, is used.

The tire vulcanization bladder is disposed inside the green tire, and when inflated, presses against the inner surface of the green tire to support the green tire from the inside and to keep the outer surface of the green tire in close contact with the inner surface of the mold. is doing.

When the tire vulcanizing bladder expands and comes into contact with the inner surface of the raw tire, an air pocket that adversely affects vulcanization may be formed between the tire vulcanizing bladder and the inner surface of the raw tire. Therefore, since the air between the green tire and the tire vulcanization bladder is released to the outside at the initial stage of vulcanization, the groove on the outer surface of the tire vulcanization bladder has a depth of 0.2 to 0.8 mm. 80 to 150
There was an article.

[0005]

However, when a groove is provided on the outer surface of the tire vulcanizing bladder, tensile stress is apt to concentrate on the groove during expansion, and the aging of the groove portion at the end of use of the tire vulcanizing bladder. However, there is a problem that it is fast (a large crack is generated compared to other parts).

Further, as shown in FIG. 5, ribs 100 corresponding to the grooves are formed on the inner surface of the tire vulcanized by using the tire vulcanization bladder having the groove. When the ribs 100 are used, the cracks 102 may be generated from the corners of the base of the rib 100, or the cracks 1 may be generated.
02, there is a problem such as biting of the tube.

In order to prevent cracks from the ribs on the inner surface of the tire, it is necessary to increase the radius of curvature of the corners of the ribs 100 as much as possible. Increasing the radius of curvature means that the groove of the tire vulcanization bladder is formed. The radius of curvature of the edge part of is to be increased. When the radius of curvature of the edge portion of the groove is increased, the raw rubber of the raw tire easily enters the groove during the pressure contact of the tire vulcanization bladder, and it becomes difficult for air to escape.

As described above, since the curvature of the edge portion of the groove has a great influence on the escape of air and the generation of cracks on the inner surface of the tire, it is extremely necessary to process the mold for vulcanizing the tire vulcanizing bladder. High precision is required. For this reason, ribs corresponding to the grooves of the tire vulcanization bladder are formed by electrical discharge machining on the inner surface of the mold for vulcanizing the tire vulcanization bladder, but the processing speed of the electrical discharge machining itself is slow, and the mold Since the inner surface is a curved surface, it takes a lot of time and labor for processing. Therefore, only the inner surface processing cost of the mold for vulcanizing the tire vulcanizing bladder is 1/3 to 1 of the manufacturing cost of the entire mold.
I had the problem of occupying / 2. In addition, the inner surface of the mold for vulcanizing the conventional tire vulcanization bladder,
The surface of the bladder for tire vulcanization was smooth so as not to cause scratches or the like.

On the other hand, at the time of vulcanizing a tire, a release agent is applied to the inner surface of the tire in order to prevent the adhesion between the tire and the bladder for tire vulcanization. There is also a problem that a large amount of the release agent is used because it is necessary to apply the release agent to all of them.

In consideration of the above facts, the present invention can improve the life of the tire vulcanizing bladder, reduce the manufacturing cost of the tire vulcanizing bladder, prevent the inner surface of the tire from cracking, and reduce the amount of the release agent used. It is an object to provide a bladder for tire vulcanization and a tire vulcanizing method.

[0011]

According to a first aspect of the present invention, there is provided an inflatable and defensible tire vulcanization bladder which is made of an elastic material and supports the tire from the inside during tire vulcanization. It is characterized in that fine irregularities are formed on the outer peripheral surface which abuts.

In the tire vulcanizing method according to the second aspect, the tire is vulcanized by supporting the tire from the inside by a tire vulcanizing bladder having fine irregularities formed on the outer peripheral surface contacting the inner surface of the tire. It has a feature.

[0013]

The bladder for tire vulcanization according to claim 1 comprises:
Since fine irregularities are formed on the outer peripheral surface that abuts the tire inner surface to be vulcanized, when the tire vulcanizing bladder expands and contacts the inner surface of the tire, the air between the tire vulcanizing bladder and the tire is The tire vulcanization bladder can support the tire from the inner surface without causing unnecessary air accumulation because it escapes through the fine irregularities.

To form fine irregularities on the outer peripheral surface of the tire vulcanizing bladder, fine irregularities may be formed on the inner surface of the mold for vulcanizing the tire vulcanizing bladder. To form fine irregularities on the inner surface of the mold, for example, shot blasting, etching or the like can be used. Here, shot blasting can easily form fine irregularities in a short time and can minimize the processing cost of the mold for vulcanizing the tire vulcanizing bladder. The manufacturing cost of the vulcanization bladder can be reduced.

Further, since the outer peripheral surface of the tire vulcanizing bladder has fine irregularities, there is no portion where stress concentrates on the outer surface during expansion. Therefore, cracks are unlikely to occur on the outer surface of the tire vulcanization bladder, and the life of the tire vulcanization bladder can be extended.

Further, in a tire having an inner surface supported by a conventional tire vulcanization bladder having a groove formed on the outer surface, there is a problem that a rib formed by the groove is formed on the inner surface of the tire and a crack is generated from the rib. But
Since the inner surface of the tire vulcanized by the tire vulcanization bladder of the present invention has a fine uneven shape, cracks are less likely to occur from the inner surface when the tire is used for running.

Further, since the outer peripheral surface of the tire vulcanizing bladder has fine irregularities, it exerts its own peeling effect to prevent adhesion to the tire to be vulcanized, and holds the release agent on the fine irregularities. It is possible to reduce the amount of the release agent used, not only the liquid and the powder, as compared with the conventional method.

The average depth of the fine irregularities of the tire vulcanizing bladder is preferably in the range of 0.05 to 1.0 mm. Here, if the average depth of fine irregularities is less than 0.05 mm,
Air between the vulcanization bladder and the inner surface of the tire becomes difficult to escape, which is not preferable, and when it exceeds 1.0 mm, a portion where stress concentrates appears and causes cracking, which is not preferable.

According to the tire vulcanizing method of the second aspect, when the tire vulcanizing bladder expands and comes into contact with the inner surface of the tire, air between the tire vulcanizing bladder and the tire is fine. The tire vulcanization bladder escapes through the irregularities and supports the tire from the inner surface without generating unnecessary air accumulation. On the inner surface of the vulcanized tire, fine irregularities that are the reverse of the fine irregularities of the tire vulcanizing bladder are formed. In the tire having the inner surface supported by the conventional tire vulcanization bladder having the groove formed on the outer surface, the rib formed by the groove is present on the inner surface of the tire, and thus there is a problem that cracks are generated from the rib. Since the inner surface of the tire vulcanized by the tire vulcanizing method described above has fine irregularities, cracks are unlikely to occur from the inner surface when the tire is used for running. That is, by the tire vulcanizing method according to the second aspect, it is possible to vulcanize a tire in which cracks are less likely to occur on the inner surface.

Further, since the tire is supported by the tire vulcanization bladder whose outer peripheral surface has fine irregularities, cracks are less likely to occur on the outer surface of the tire vulcanization bladder, and the tire vulcanization bladder is less vulnerable than the conventional one. Since the life of the tire can be extended, the frequency of replacement of the tire vulcanizing bladder can be reduced, and the efficiency of the tire vulcanizing process can be improved.

Further, since the outer peripheral surface of the tire vulcanizing bladder has fine irregularities, it exerts a peeling effect by itself for preventing the adhesion to the tire to be vulcanized, and the release agent has fine irregularities. It becomes possible to retain the amount of the release agent used in the vulcanization process, and it is possible to reduce the amount of the release agent used in comparison with the conventional method.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS.

FIG. 1 shows the bladder 10 in the free state. The bladder 10 of this embodiment is a so-called open-end type bladder having a ring shape.

The bladder 10 is provided with a pair of openings 12 that are open in the axial direction at both ends in the axial direction (direction of arrow A in FIG. 1).

The opening 12 is substantially defined by a metal fitting tightening margin 14 having a substantially pentagonal cross section and formed in a ring shape.

An inflatable cylindrical bladder body 16 is integrally extended between the metal fitting tightening margins 14. The material of the bladder body 16 may be butyl rubber or the like.

The bladder body 16 includes metal fitting tightening margins 14A, 1
4B and a shoulder 18 extending radially outward from the shoulder 4 and the shoulder 1
8 from the first inclined portion 20, a curved portion 21 extending outward of the first inclined portion 20 and having a center of curvature radially outward, and expanded from the curved portion 21. The second inclined portion 22 that inclines in the direction of
And a curved portion 24 that is provided at the central portion in the axial direction and that has the center of curvature inside.

Random fine irregularities 26 as shown in FIG. 2 are formed on the outer peripheral surface of the bladder body 16.

The fine irregularities 26 are formed by providing fine irregularities on the inner surface of a mold (not shown) for vulcanizing the bladder 10. As a method for forming fine irregularities on the inner surface of the mold, so-called shot blast for hitting steel shot or the like to form fine irregularities or etching for irregularities by corrosion can be used.

Needless to say, fine irregularities may be formed on the inner surface of the mold by a method other than the above, but the method of forming fine irregularities by shot blasting is easy to process, workability, and cost. preferable. In this embodiment, fine irregularities are formed by shot blasting on the inner surface of the mold for vulcanizing the bladder 10.

The average depth D of the fine irregularities 26 of the bladder 10 is preferably in the range of 0.05 to 1.0 mm.

Next, the vulcanization process of the green tire by the bladder 10 of this embodiment will be briefly described. The vulcanizer 30 includes an upper mold 32 and a lower mold 34, and the bladder 10 is arranged above the center of the lower mold 34. The bladder 10 has metal fitting tightening margins 14A and 14B.
Are fixed to the ring-shaped fittings 36 and 38, respectively. The upper mounting member 36 is attached to a center post 40 that expands and contracts by a cylinder (not shown), and the lower mounting member 38 is attached to a fixing member 42 arranged in the central portion of the lower mold 34. The fixing member 42 is provided with, for example, a fluid passage (not shown) for introducing air into the bladder 10.

Here, the raw tire 46 is the lower mold 34.
When the air is introduced into the bladder 10, the bladder 10 expands and presses against the inner surface of the green tire 46, and then the upper mold 32 and the lower mold 34 are connected as shown in FIG. Then, the green tire 46 is closed, the vulcanizing fluid is introduced into the bladder 10, and the upper mold 32 and the lower mold 34 are heated for vulcanization.

Here, when the bladder body 16 expands and comes into contact with the inner surface of the raw tire 46, the air between the bladder body 16 and the inner surface of the raw tire 46 passes through the concave portions of the fine irregularities 26 to the outside. Is discharged. After that, when the bladder body 16 further expands and comes into pressure contact with the inner surface of the raw tire 46, fine unevenness corresponding to the fine unevenness 26 of the bladder 10 is formed on the surface of the inner rubber (inner liner) of the raw tire 46. Become.

Here, the fine irregularities 26 of the bladder 10 are
Since the average depth is in the range of 0.05 to 1.0 mm and is random, stress does not concentrate on the bladder body 16 during expansion, and cracks are unlikely to occur from the bladder body 16.

Further, even if cracks occur due to the aging of rubber, the fine irregularities 26 do not have directionality, so the growth of cracks is extremely small, and for example, the life can be increased by about 20% compared to the conventional case ( (See FIG. 4). This allows the bladder 1
The replacement frequency of 0 can be reduced, and the tire manufacturing cost can be reduced.

Also, unlike the electric discharge machining, the bladder 10
Since the fine concavo-convex for molding the fine concavo-convex 26 can be easily and quickly processed by shot blasting or the like in the mold for vulcanizing, the cost of the mold for vulcanizing the bladder 10 (mainly the inner surface machining cost) is significantly increased. Therefore, the manufacturing cost of the bladder 10 can be reduced.

Further, a release agent (for example, a powdery release agent such as mica powder or a liquid release agent such as silicon oil) is applied to the surface of the bladder 10 so that the bladder 10 and the green tire 46 are not adhered to each other. In addition to the fact that the fine unevenness of the surface itself exerts a peeling effect, the release agent enters the fine unevenness 26 and is held in a predetermined amount, so that the adhesion preventing effect is sufficient even if the usage amount (or the number of times of use) of the release agent is reduced. Therefore, it is possible to save about 1/3 of that of the conventional one.

The inner surface of the tire after vulcanization is the bladder body 16
The portion that is pressed into contact with the surface has fine irregularities. Since the fine irregularities on the inner surface of the tire have a shape in which the fine irregularities 26 of the bladder 10 are inverted, the average depth is in the range of 0.05 to 1.0 mm.

Here, if the bladder has a recess such as a groove, when the bladder is pressed against the inner liner of the raw tire, the raw rubber that abuts on the recess is locally flown, and is adjacent to the inner liner. Disordered carcass cord arrangement (so-called cord sucking phenomenon)
However, in the past, the gauge of the inner liner was set to be thick to prevent the carcass cord from being disturbed. However, since the surface of the bladder 10 of the present embodiment has fine irregularities, the rubber of the inner liner does not locally flow when it is pressed against the green tire 46.
Therefore, the gauge of the inner liner of the tire to be vulcanized can be made thinner than before, and the amount of rubber used in the tire can be reduced. As a result, the weight and cost of the tire can be reduced.

Further, since the inner surface of the tire has fine irregularities, there is a risk of cracks such as those generated from the rib portion, which is a problem in a tire having ribs (marks of air venting grooves) formed on the inner surface. Absent.

As the bladder body 16 expands,
The fine irregularities 26 are extended in the plane direction, and the average depth D becomes shallow. Further, since the bladder body 16 has a different amount of tension depending on its part, the depth of the fine irregularities 26 when expanded may be partially different. Therefore, the average depth D of the fine concavities and convexities 26 does not have to be constant over the entire bladder 16, and the size of the fine concavities and convexities 26 may be appropriately changed depending on the site.

For example, when the contact with the inner surface of the tire is started from the center portion of the bladder body 16 (see FIG. 1, the vicinity of the curved portion 24), the fine unevenness 26 has a bead portion (first inclined portion) from the center portion. It is preferable to increase the average depth D toward the portion corresponding to (about 20) from the viewpoint of the efficiency of the air flow. In this case, the average depth D of the fine irregularities 26 may be changed smoothly or may be changed stepwise.

Further, considering the stress at the time of expansion, it is preferable that the shape of the concave portions of the fine concavo-convex 26 is a spherical surface as smooth as possible.

The average depth D of the fine irregularities 26 is 0.0.
If it is less than 5 mm, the air flow is deteriorated, and if it is more than 1 mm, the flow of the rubber of the inner liner is affected, or a portion where stress concentrates when the bladder 10 expands is not preferable.

In this embodiment, the shape of the fine irregularities 26 is a random shape, but, for example, fine peaks having a smooth curved surface may be regularly arranged at a predetermined pitch.

In the above embodiment, the present invention has been described by taking the example of the open end type bladder, but the present invention is not limited to this, and other types such as a closed end type bladder having one end opened. Of course, the present invention may be applied to a bladder.

[0048]

As described above, the bladder for tire vulcanization according to claim 1 has fine irregularities formed on the outer peripheral surface which abuts the inner surface of the tire, and therefore has the following excellent features (1) to (4). Have an effect. (1) Since fine irregularities can be formed on the inner surface of the mold for vulcanizing the tire vulcanizing bladder by inexpensive processing such as shot blasting, the cost of the mold for molding the tire vulcanizing bladder can be minimized. Therefore, the manufacturing cost of the tire vulcanization bladder can be reduced. (2) Since the outer peripheral surface of the tire vulcanizing bladder has fine irregularities, there is no site where stress is concentrated on the outer surface during expansion, cracks are less likely to occur on the outer surface, and the life is extended. (3) Since the inner surface of the tire vulcanized by the tire vulcanization bladder of the present invention has a fine uneven shape, there is no site where stress is concentrated on the inner surface, and cracks are less likely to occur from the inner surface when the vehicle is used for running. . That is, according to the tire vulcanizing method of the present invention, it is possible to manufacture a high-quality pneumatic tire in which cracks hardly occur on the inner surface. (4) Since the release agent for preventing adhesion to the tire to be vulcanized can be held on the fine irregularities, the use amount of the release agent can be thinned compared to the conventional amount, not limited to liquid or powder.

According to the tire vulcanizing method of the second aspect, the following excellent effects (1) to (3) are obtained. (1) Since the outer peripheral surface of the tire vulcanization bladder has fine irregularities, there is no site where stress concentrates on the outer surface during expansion, cracks are less likely to occur on the outer surface, and the life is extended compared to conventional cases. Therefore, the frequency of exchanging the tire vulcanization bladder is reduced, and the efficiency of the tire vulcanization process can be improved. (2) At the time of tire vulcanization, the tire to be vulcanized is supported from the inside by the tire vulcanization bladder having fine irregularities formed on the outer peripheral surface that abuts the inner surface of the tire.
The inner surface of the vulcanized tire becomes a fine uneven shape, and there is no portion where stress is concentrated, and cracks are less likely to occur from the inner surface when the tire is used for running. That is, it is possible to manufacture a high-quality pneumatic tire in which cracks hardly occur on the inner surface. (3) Since the outer peripheral surface of the tire vulcanizing bladder has fine irregularities, it is possible to hold the release agent for preventing adhesion to the tire to be vulcanized on the fine irregularities, and to use a liquid in the vulcanization step, The amount of release agent used is not limited to powder, and the amount of release agent used can be reduced in comparison with the conventional one.

[Brief description of drawings]

FIG. 1 is a sectional view taken along the axis of a bladder according to an embodiment of the present invention.

FIG. 2 is an enlarged view of the surface of the bladder.

FIG. 3 is a schematic view showing the internal structure of a vulcanizer equipped with the bladder of this embodiment.

FIG. 4 is a graph illustrating the difference in service life between the conventional product and the product of the present invention.

FIG. 5 is an enlarged view of an inner surface of a tire molded by a conventional bladder having a groove.

[Explanation of symbols]

 10 bladder 26 fine unevenness

Claims (2)

[Claims] 1. A bladder for tire vulcanization, which is made of an elastic material and supports the tire from the inside when vulcanizing the tire, wherein fine ruggedness is formed on the outer peripheral surface that abuts the inner surface of the tire. Bladder for tire vulcanization. 2. A tire vulcanizing method, characterized in that, during tire vulcanization, the tire is supported from the inside by a tire vulcanizing bladder having fine irregularities formed on the outer peripheral surface that abuts the inner surface of the tire.