JP2006095753A - Tire vulcanizing bladder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tire vulcanizing bladder capable of reducing the defectiveness caused by a vulcanizing process especially in a tire low in flatness. <P>SOLUTION: The tire vulcanizing bladder 10 is formed of an elastic material to support the tire from the inside at the time of vulcanization of the tire and characterized in that the thickness (W1) of the part 14a, which is ranged from the hump part 24 being the end part of a tread part 1 to a buttless part 25 becoming the maximum width of the tire in a cross section including a tire rotary axis is larger than the thickness (W2) of another part 14b when the tire vulcanizing bladder 10 is expanded to be closely brought into contact with the inner surface of the tire. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an inflatable tire vulcanization bladder formed of an elastic material and supporting the tire from the inside during tire vulcanization, and more particularly to a tire vulcanization bladder applied to a tire having a low aspect ratio of 50% or less. About.

  In the production process of pneumatic tires, particularly in the vulcanization process of unvulcanized tires, green tires (unvulcanized tires or green tires) in which tire components are incorporated are usually placed in a mold, and further, A rubber bag made of a cylindrical ring having a circular or horseshoe-shaped cross section called a vulcanization bladder is inserted into the cavity. Next, an internal pressure fluid such as steam or pressurized hot water is introduced into the vulcanization bladder, and the green tire is strongly pressed against the mold and simultaneously heated from the inside. At the same time, by heating the mold with steam or the like, heating from the outside is also performed, and the green tire is vulcanized.

  In the tire vulcanization bladder 110, as shown in FIG. 4, the portion in contact with the green tire has the same portion in the range from 4.0 to 8.0 mm from the center portion near the tire equator line to the tire side portion. It is thickness (W), and the part which corresponds to a tire bead part from a tire side part is formed so that it may become thick gradually (for example, refer to patent documents 1).

In addition, the vulcanization bladder for tires has a ridge, and the thickness of the ridge portion is thicker than other portions, but this portion is considered as an exception.
JP 2002-137227 A

  The size of the tire vulcanization bladder used at the time of vulcanization molding is set according to the peripheral length in the width direction and the circumferential direction inside the green tire. For example, the tire vulcanization bladder is set such that the peripheral length of the green tire × ± 10% = the peripheral length of the vulcanization bladder.

  When such a tire vulcanization bladder is set, a shaping internal pressure (for example, 1300 kPa) is applied, and the tire is inflated, the green tire has a shape close to a natural equilibrium shape. At this time, particularly in a tire having a low flatness ratio, the mold touch with respect to the shoulder portion is delayed from the mold touch with respect to the other portions, which causes defects such as bear generation.

  In view of the above problems, an object of the present invention is to provide a tire vulcanization bladder that can reduce defects caused by a vulcanization process, particularly in a tire having a low flatness.

  In order to solve the above-mentioned problems, the present invention is characterized by an inflatable tire vulcanization bladder formed of an elastic material and supporting the tire from the inside during tire vulcanization, and inflates and adheres to the inner surface of the tire In this case, the thickness of the portion from the hump portion which is the end portion of the tire tread portion to the buttress portion having the maximum tire width in the cross section including the tire rotation axis is thicker than the thickness of the other portions. The gist is that it is a vulcanizing bladder for tires.

  According to the tire vulcanization bladder according to the feature of the present invention, the mold touch on the shoulder portion is performed earlier or substantially simultaneously with the mold touch on the other portion, and the occurrence of defects such as bear generation due to the vulcanization process is reduced. be able to.

  In the tire vulcanization bladder according to the feature of the present invention, the difference between the thickness of the portion corresponding to the hump portion and the buttress portion and the thickness of the other portion is 5 to 30 mm in a free state where no internal pressure is applied. It is preferable. This is because if the difference in thickness is smaller than 5 mm, the effect for reducing defects is small, and if it exceeds 30 mm, it is difficult to swell even when pressure is applied to the vulcanizing bladder for tires.

  Further, the tire vulcanization bladder according to the feature of the present invention is preferably applied during vulcanization of a tire having a flatness ratio of 50% or less. This is because, in such a tire having a low flatness ratio, when a conventional tire vulcanization bladder is applied, a time difference occurs between the mold touch on the shoulder portion and the mold touch on the other portion.

  ADVANTAGE OF THE INVENTION According to this invention, the tire vulcanization bladder which can reduce the defect resulting from a vulcanization | cure process especially in a tire with a low flatness ratio can be provided.

  Next, embodiments of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic and ratios of dimensions and the like are different from actual ones. Accordingly, specific dimensions and the like should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

(Vulcanized bladder for tires)
An inflatable tire vulcanizing bladder for supporting a tire from the inside during tire vulcanization according to an embodiment of the present invention will be described with reference to FIG.
FIG. 1 shows a tire vulcanizing bladder 10 in a free state where no internal pressure is applied. The tire vulcanization bladder 10 according to the present embodiment is a so-called open-end bladder that has a ring shape.
Further, the tire vulcanizing bladder 10 includes flange portions 12 having openings that are open in the axial direction at both ends in the axial direction (the direction of arrow A in FIG. 1). Between the one flange portion 12 and the other flange portion 12, an expandable cylindrical bladder body 14 is integrally extended. Examples of the material of the vulcanizing bladder for tire 10 include butyl rubber.
When the tire vulcanization bladder 10 expands and adheres closely to the inner surface of the tire, the tire vulcanization bladder 10 has a portion 14a corresponding to the buttress portion that is the end of the tread portion and the buttress portion that has the maximum tire width in the cross section including the tire rotation axis. The thickness (W1) is thicker than the thickness (W2) of the other portion 14b.

  The difference (W1−W2) between the thickness (W1) of the portion 14a from the hump portion to the buttress portion and the thickness (W2) of the other portion 14b is 5 to 30 mm in the free state.

(Pneumatic tire manufacturing method)
Next, a method for manufacturing a pneumatic tire to which the tire vulcanizing bladder 10 according to the present embodiment is applied will be described with reference to FIG. In FIG. 2, only the left one side is shown, but it is of course that it is normally symmetrical.

  First, in a vulcanization process of an unvulcanized tire, a green tire 22 (an unvulcanized tire or a raw tire) in which a tire constituent member is incorporated is placed in a mold 20 and further vulcanized for the tire in a lumen of the green tire. The bladder 10 is inserted.

  Next, an internal pressure fluid such as steam or pressurized hot water is introduced into the tire vulcanization bladder 10, and the green tire 22 is strongly pressed against the mold 20 and simultaneously heated from the inside. FIG. 2 shows a state where the tire vulcanization bladder 10 presses the green tire 22 against the mold 20.

  The green tire 22 used here is a low flat rate tire having a flat rate of 50% or less. The green tire 22 includes a tread portion 1, a sidewall portion 2 continuous to the tread portion 1, and a bead portion 8 that continues to the inside of the sidewall portion 2 in the tire radial direction. The carcass layer 3 extends in a toroid shape between the bead cores 4 embedded in the pair of bead portions 8, and is wound around the bead core 4 from the inner side to the outer side along the circumferential surface thereof. Consists of carcass plies. The carcass ply is formed by embedding an organic fiber cord covered with rubber. The belt layer 6 is disposed outside the carcass layer 3 in the tire radial direction, and is formed by embedding a steel cord covered with rubber. Here, two belt layers 6 are provided.

  Further, as described above, when the tire vulcanization bladder 10 expands and comes into close contact with the inner surface of the tire, the tire maximum width in the cross section including the tire rotation axis from the hump portion 24 that is the end portion of the tread portion 1. The thickness of the portion 14a corresponding to the buttress portion 25 is thicker than the thickness of the other portion 14b. For this reason, in FIG. 2, the mold touch on the shoulder portion is performed earlier or almost simultaneously with the mold touch on the other portion.

(Function and effect)
Conventional vulcanization bladders for tires differ in shape between the green tire and the mold at the shoulder portion of the tire during vulcanization molding.

  For this reason, in this embodiment, as shown in FIG. 2, the rubber gauge of the tire vulcanization bladder 10 corresponding to the shoulder portion of the green tire 22 is increased. When the internal pressure is applied, the inner surface of the tire vulcanization bladder is close to the natural equilibrium shape, so the shape of the outer surface of the tire vulcanization bladder in contact with the green tire is a shape that protrudes only in the part where the rubber gauge is thick. Become.

Therefore, the difference between the shape of the green tire 22 and the shape of the mold 20 is reduced,
The mold touch on the shoulder portion is performed earlier or almost simultaneously than the mold touch on the other portion. For this reason, defects, such as bear generation resulting from a vulcanization process, can be reduced.

  Further, in the tire vulcanization bladder 10 according to the present embodiment, the difference between the thickness of the portion corresponding to the hump portion 24 to the buttress portion 25 and the thickness of the other portion is 5 to 30 mm in a free state where no internal pressure is applied. It is. This is because if the difference in thickness is smaller than 5 mm, the effect for reducing defects is small, and if it exceeds 30 mm, it is difficult to swell even when pressure is applied to the vulcanizing bladder for tires.

  Further, the tire vulcanization bladder 10 according to the present embodiment is particularly suitably applied when vulcanizing a tire having a flatness ratio of 50% or less. This is because, in such a tire having a low flatness ratio, when a conventional tire vulcanization bladder is applied, a time difference occurs between the mold touch on the shoulder portion and the mold touch on the other portion.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.

  In order to confirm the effect of the present invention, tire vulcanization bladders according to Conventional Example 1 and Example 1 were experimentally manufactured.

  Conventional Example 1 has the conventional shape shown in FIG. 4, and the thickness of the bladder main body 114 was uniform. Further, the peripheral length in the tire width direction of the tire vulcanization bladder according to Conventional Example 1 was 359 mm, and the outer diameter of the bladder was 506 mm.

  Example 1 has the shape shown in FIG. 1, and the thickness (W1) of the portion 14a in the width of 50 mm (L3) from the position 70 mm (L2) from the center in the tire width direction (CL) and the thickness of the other portion 14b. Compared with (W2), it was set to plus 10 mm. The peripheral length (L1) in the tire width direction of the vulcanizing bladder for tires according to Conventional Example 1 was 359 mm, and the outer diameter of the bladder was 506 mm.

  The tire vulcanization bladder according to Conventional Example 1 and Example 1 was applied to perform vulcanization molding of the green tire, and the defect occurrence rate of each green tire was confirmed.

  The size of the green tire was PSR 225 / 40R18, the peripheral length inside the tire width direction was 343 mm, and the tire inner diameter was 604 mm.

  Moreover, the defect occurrence rate was represented by the bear occurrence rate in the shoulder portion of the tire after vulcanization molding.

(result)
The results are shown in Table 1.

  In Example 1, the defect occurrence rate is lower than that in Conventional Example 1. For this reason, it was confirmed that defects caused by the vulcanization process can be reduced by increasing the rubber gauge of the tire vulcanization bladder corresponding to the shoulder portion of the green tire.

  Further, when the bear occurrence rate (defect occurrence rate) when the thickness of the tire vulcanization bladder according to Example 1 was changed, the result shown in FIG. 3 was obtained.

  According to FIG. 3, it was found that when the thickness of the tire vulcanization bladder is set to 5 to 30 mm, the bear generation rate is particularly lowered.

It is sectional drawing of the vulcanization bladder for tires concerning embodiment. It is sectional drawing including a tire rotating shaft center which shows the internal structure of the vulcanizer which set the vulcanization bladder for tires concerning embodiment. It is a graph which shows the result of the defect incidence rate which concerns on an Example. It is sectional drawing of the conventional vulcanization bladder for tires.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Tread part, 2 ... Side wall part, 3 ... Carcass layer, 4 ... Bead core, 6 ... Belt layer, 8 ... Bead part, 10 ... Tire vulcanization bladder, 12 ... Flange part, 14 ... Bladder main body, 20 ... Mold, 22 ... Green tire, 24 ... Hump part, 25 ... Buttress part

Claims (3)

An inflatable tire vulcanization bladder formed of an elastic material and supporting the tire from the inside during tire vulcanization,
When inflating and closely contacting the inner surface of the tire, the thickness of the portion from the hump, which is the end of the tire tread, to the buttress, which is the maximum width of the tire in the cross section including the tire rotation axis, is the thickness of the other portion. Tire vulcanization bladder characterized by being thicker.   2. The tire use according to claim 1, wherein the difference between the thickness of the portion corresponding to the hump portion and the buttress portion and the thickness of the other portion is 5 to 30 mm in a free state where no internal pressure is applied. Vulcanizing bladder. The tire vulcanization bladder according to claim 1, wherein the tire vulcanization bladder is applied during vulcanization of a tire having a flatness ratio of 50% or less.

Images