JPH04275108A - Bladder for vulcanization of tire - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tire vulcanizing bladder that is installed in a tire vulcanizer and applies internal pressure and heat from inside the tire during vulcanization.

0002

[Prior Art] As shown in Fig. 6, a tire vulcanizer has a
A mold (10) corresponding to the outer circumference of the tire is equipped with a thin rubber bag called a bladder (11) that provides the tire with the internal pressure and heat necessary for tire vulcanization. It is designed to carry out sulfurization. This bladder (
As shown in FIG. 7, grooves (12) are formed on the outer surface of 11) from the center toward both ends to vent air during vulcanization.

[0003] In recent years, there has been a trend toward flattening and widening radial tires in order to improve their maneuverability and stability. For example, the aspect ratio (tire height H
/tire width W) of 75 to 40% has appeared.

0004

[Problems to be Solved by the Invention] However, the flatter the tire becomes, the more likely it is that defects due to air pockets will occur in the shoulder portion of the tire. This is because during the shaping process during tire vulcanization, the contact of the bladder, which expands due to internal pressure, with the inner periphery of the shoulder portion is delayed.

That is, as shown in FIG. 8, the conventional bladder has been improved to some extent by increasing the thickness of the crown region (13) corresponding to the inner periphery of the crown (T3) of the tire (T). Although the bladder (11) is inflated in a flat shape to match the shape of the tire, the bladder (11) contacts the tire (T) first with the crown region (13) of the bladder (11), and then with the tire at the end. From approximately the center of the sidewall part (T6), which becomes large, to the bead end (T7
) is in contact with the vicinity of the bead region (15) that corresponds approximately to the inner periphery of the bead portion (T5), and the vicinity of the shoulder portion (T4) from the side edge of the crown portion to approximately the center of the sidewall portion (T6). The shoulder region (14), which corresponds to the inner periphery of the contact region, is the last to contact, and the contact pressure is also the lowest in the shoulder region (14), making it easy for air to concentrate in this region.

[0006] For this reason, on the outer surface of the bladder (11),
Although grooves (12) are formed to bleed air as shown in FIG. 7, their functions and effects are not sufficiently achieved, and air tends to accumulate in the shoulder portion of the tire. Such a problem is caused by an oblateness ratio of 60%.
This is noticeable in the following tires.

[0007] In order to solve the above-mentioned problems, it is preferable to change the stiffness distribution of the bladder to hasten the contact of the shoulder region with the tire. As a means for this, it is possible to reduce the rigidity of the shoulder region by changing the material of the crown region, the shoulder region, and the bead region, or by changing the thickness.

However, in either case, it is technically extremely difficult to actually manufacture the bladder, and it is also difficult to adapt it to the delicate shape of the tire.

In view of the above, the present invention has been made by focusing on the fact that the outer surface of the bladder is provided with grooves for air release, and the distribution of these grooves is changed for each region. In this way, the stiffness of the shoulder region is reduced to promote bulge in this region, thereby speeding up contact with the tire and preventing defects due to air pockets during tire vulcanization.

0010

[Means for Solving the Problems] The present invention is a tire vulcanizing bladder having a groove for air release formed on the outer surface of the bladder. On the surface, a crown region approximately corresponds to the inner circumference of the crown portion of the tire, a shoulder region approximately corresponds to the inner circumference from the side edge of the crown portion to approximately the center of the sidewall portion having the maximum width of the tire, and a shoulder region of the sidewall portion. The distribution form of the grooves is different in the bead region approximately corresponding to the inner periphery from the approximate center to the bead end, and the volume ratio of the grooves in each region is 100 in the crown region and 1000 or more in the shoulder region, Bead area 5
It is characterized by being set to 00 or less.

[0011]

[Function] According to the tire vulcanizing bladder of the present invention constructed as described above, the volume ratio of the groove in the shoulder region of the tire is much larger than that in the crown region.
Because it is more than twice as large and larger than the bead region, this shoulder region has lower rigidity than other regions, and bulge is more likely to be promoted, so in the shaping process during tire vulcanization, The shoulder region of the bladder, which expands due to internal pressure, comes into contact with the inner periphery of the tire substantially at the same time as the crown region, or even if slightly later than the crown region, earlier than the bead region. Further, for this reason, internal pressure acts strongly in this shoulder region, contact pressure also becomes high, and air is easily discharged.

0012

Embodiments Next, embodiments of the present invention will be explained based on the drawings.

FIGS. 1 to 3 show embodiments in which the grooves on the outer surface of the bladder have different distributions, and FIG. 4 shows the inflated state of the bladder of the present invention.

In the figure, (1) shows a bladder according to the present invention made of a thin rubber bag, which is used in a tire vulcanizer as shown in FIG. 6, and applies internal pressure and heat to the inside of the tire during tire vulcanization. (2) shows a groove for venting air formed on the outer surface of the bladder (1).

The outer surface of the bladder (1) has a crown region (3) that approximately corresponds to the inner periphery of the crown region (T3) of the tire (T), and a region extending from the side edge of the crown region (T3) to the furthest part of the tire. A shoulder region (4) approximately corresponds to the inner periphery near the shoulder portion (T4) up to approximately the center of the sidewall portion (T6), which has a large width, and the sidewall portion (T6).
The bead region (5) approximately corresponds to the inner circumference near the bead (T5) from the approximate center of the bead (T6) to the bead end (T7).
), and the distribution form of the groove (2) is different for each region (3) (4) (5) as shown in FIGS. 1 to 3, and each region (3) (4) (5) The volume ratio of groove (2) of
In other words, the ratio of the volume of the space occupied by the groove (2) is set to 100 for the crown region (3), 1000 or more for the shoulder region (4), and 500 or less for the bead region (5).

[0016] The volume ratio is set depending on the tire size, aspect ratio, etc., but if the shoulder area (4) is 100%
If it is less than 0, the effect of speeding up the contact of this part with the tire will be small, and if the bead area (5) exceeds 500, the contact of the bead area with the tire will be faster, and the expected effect will not be obtained. I can't do it.

As for the distribution form of the grooves (2) having different volume ratios as described above, the number of grooves in the diagonal direction toward both ends is determined in each region (3), (4), and (5) as shown in FIG. As shown in FIG. 2, a groove that intersects with the groove in the shoulder region (4) may be added to the shoulder region (4) based on the diagonal groove toward both ends, or as shown in FIG. 3, the groove in the shoulder region (4) It is possible to implement various forms in which the volume ratio can be changed by changing the number and density of grooves in each area (3), (4), and (5), such as adding circumferential grooves to the area.

FIG. 5 illustrates the cross-sectional shape of the groove (2), in which (A) shows the width of the groove opening, (B) shows the width of the bottom, and (C) shows the depth. For example, the thickness (t) of the bladder (1) is usually about 3 to 5 mm, and in that case, A
is (1.0±0.3)mm, B is (0.6±0.3)m
m and C are (0.4±0.2) mm.

The volume of the groove (2) in each region in the above is (S×C) when the area occupied by the groove (2) on the surface of each region is (S), and the volume of the groove (2) in each region is (S×C).
) becomes [(A+B)/2×stated length of groove].

According to the bladder (1) constructed as described above, the stiffness of the shoulder region (4) is higher than that of the other regions (3) (5).
), and the shoulder area (4)
The swelling is promoted as shown in FIG. 4, and the swelling becomes faster. Therefore, during the shaping process during tire vulcanization, the shoulder region (4) of the bladder (1), which expands due to internal pressure, comes into contact with the tire (T) earlier, and the shoulder region (4) comes into contact with the tire (T) almost simultaneously, or at the same time as the crown region (3). region(
Even if it is slightly later than 3), it will come into contact with the inner circumference of the tire earlier than in the bead region (5), and the contact pressure will also be stronger in this shoulder region (4). Therefore, the air removal effect by the grooves (2) on the outer surface is also promoted, and no air pockets are generated in the shoulder portion (T4) of the tire (T).

Table 1 below shows the results of a tire vulcanization test using the bladder of the present invention and a conventional product.

Here, the conventional product in the table uses a bladder with the groove distribution form shown in FIG. 7, Example 1 uses a bladder with the groove distribution form shown in FIG. 2, and Example 2 uses a bladder with the groove distribution form shown in FIG. This is what I did. Further, Comparative Examples 1 and 2 show cases in which bladders having the groove distribution forms shown in FIGS. 2 and 3 and whose volume ratios are outside the range of the present invention are used.

[0023]The tire size is 205/55R16.
200 pieces of each were vulcanized. The bladder used in the test had a thickness (t) of 4 mm, a groove width (A) of 0.6 mm, and a depth (C) in the groove cross section (Fig. 5).
) 0.4 mm.

[0024]

[Table 1]

As is clear from the above results, vulcanization using the bladder of the present invention was found to be effective without causing defects due to air pockets.

[0026]

Effects of the Invention As described above, according to the bladder of the present invention, the stiffness of the shoulder region is lowered to make it easier to swell due to the change in the distribution form of the grooves on the outer surface. The contact with the tire becomes faster and the contact pressure becomes higher, allowing air to be discharged better and preventing defects caused by air pockets. Moreover,
Since it is only necessary to change the distribution form of the grooves on the outer surface, the bladder is easy to manufacture and implement.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the distribution form of grooves in a bladder according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a groove distribution form of a bladder in another embodiment.

FIG. 3 is an explanatory diagram showing yet another groove distribution form of a bladder.

FIG. 4 is a schematic cross-sectional view showing an inflated state of the bladder of the present invention.

FIG. 5 is an enlarged cross-sectional view of the groove.

FIG. 6 is a schematic cross-sectional view illustrating a tire vulcanizer equipped with a bladder.

FIG. 7 is an explanatory diagram showing the groove distribution form of a conventional bladder.

FIG. 8 is a schematic cross-sectional view showing a conventional bladder in an inflated state.

[Explanation of symbols]

(1) Bladder (2)...Groove (3)……Crown area (4)...Shoulder area (5)...Bead area (T)...Tire (T3)...Crown part (T4)...Shoulder part (T5)...Bead part

Claims (1)

[Claims] 1. A bladder for tire vulcanization having a groove for air release formed on the outer surface of the bladder, the outer surface of the bladder having a crown region approximately corresponding to the inner periphery of the crown portion of the tire. a shoulder region that substantially corresponds to the inner periphery from the side edge of the crown portion to the approximate center of the sidewall portion of the tire at its maximum width; and a bead portion that substantially corresponds to the inner periphery from the approximate center of the sidewall portion to the bead end. The distribution form of the grooves is different depending on the region, and the volume ratio of the grooves in each region is set to 100 in the crown region, 1000 or more in the shoulder region, and 500 or less in the bead region. Bladder for curing tires.