JPH0957755A - Mold for vulcanizing tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a tire with a good air flow property, free from the occurrence of tire surface defects (bare) due to air concentration, and having high quality narrow width grooves in regard of the improvement of a tire vulcanizing mold with a number of blades planted for forming narrow width grooves in the tread part of a tire. SOLUTION: A small hole 11 is provided in the proximity of the tread outer contour forming surface 4 of a mold 2 for a blade 3, and also provided is a narrow width slit 5 that establishes communication between the small hole 11 and blade tip end 3A, the width of the small hole 11 being made larger than that of the slit 5. Since the small hole 11 with a large volume is set at the just front position of mold clamping, air flow property is high, discharge of stayed air is done effectively, and the occurrence of bare can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tire vulcanizing mold for vulcanizing a green tire to produce a product tire, for forming a narrow groove such as a sipe in a tread portion of the product tire. The present invention relates to an improvement of a tire vulcanizing mold in which a large number of blades are planted in the tread forming portion.

[0002]

2. Description of the Related Art Conventionally, when a large number of narrow grooves such as sipes are arranged in a tread portion of a tire, braking performance can be improved by an edge effect. For example, studless tires on wet road surfaces, tires for all seasons, etc. Narrow grooves such as sipes are often used in product design in order to obtain braking performance.

Such a narrow groove is formed by using an actual open flat plate 5-7670.
No. 7, JP-A-5-57728, a number of blades with slits are planted in the tread forming portion of the tire vulcanizing mold, and these blades are used to tread the product tire. It is formed.

With reference to FIG. 3, a tire vulcanizing mold provided with this conventional blade will be described.

Reference numeral 2 is a die, 3 is a blade for forming a narrow groove, and the blade 3 is planted in a tread forming portion of the die and fixed to the die. Reference numeral 3B denotes a portion where the blade is planted in the mold, and 4 denotes a tread outer contour forming surface of the mold.

The mold has an air bleeding function for discharging the air trapped between the green tire and the mold to the outside of the mold while closing the mold. However, in order to form a large number of narrow grooves in the tire tread portion, a large number of the blades are used by being planted in a mold.
However, when the mold is closed and bites into the green tire, it is difficult for air to escape to the outside of the mold, which causes a defect due to an air pocket on the surface of the vulcanized product tire. This defect, called bare, impairs the appearance of the product tire and significantly reduces the commercial value. Therefore, the blade 3 is provided with a slit 5 having a narrow width.
The air can penetrate through the blade, the fluidity of the air can be obtained, and the function of the air bleeding provided in the mold can be exerted.

[0007]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention As shown in FIG.
The conventional slit 5 extends in the direction normal to the tread outer contour forming surface 4, and is formed with an opening 7 at the blade tip 3A and an arc R having a diameter of the slit on the side of the metal mold implanted. It has an end section 9.

However, since the diameter of the arc R of the final portion 9 is small, air is likely to accumulate in the final portion 9 during vulcanization, and the air pool causes the air to accumulate on the surface of the tread land portion of the vulcanized product tire in the vicinity. It causes bears and significantly reduces the commercial value.

Further, when the product tire is mounted on a vehicle and is repeatedly driven, the tread portion is repeatedly subjected to strain, and the strain becomes greater as it approaches the tread surface. Since the radius of curvature of the slit end portion 9 is small, this strain concentrates at the tip of the rubber meat portion formed by the end portion 9 close to the tread surface and causes a crack early.

An object of the present invention is to solve such a problem, and it is possible to manufacture a tire having a large number of narrow grooves of high quality in which bears are not generated due to air accumulation. A mold for tire vulcanization is provided.

[0011]

In order to achieve the above object, the present invention according to claim 1 is a tire vulcanizing mold in which a large number of blades for forming narrow grooves are planted in a tread portion of a tire. In, the blade has a small hole provided in the vicinity of the tread outer contour forming surface of the mold, and has a narrow width slit communicating from the small hole to the blade tip, the width of the small hole of the slit It is assumed to be larger than the width.

By forming a small hole in the vicinity of the tread outer contour forming surface of the mold, since a small hole having a large volume exists immediately before the mold is closed, high air fluidity is obtained and the mold is provided. The air bleeding function can be fully exerted, and the generation of bears due to the accumulation of air is suppressed.

Further, as a product tire after vulcanization, a rubber meat portion having a relatively large rubber volume is brought in the vicinity of the surface of the tread land portion by the small holes of the slits, and cracks do not occur at an early stage.

The present invention according to claim 2 is directed to claim 1
The die according to the above item 1, characterized in that the slit extends obliquely with respect to a normal to the tread outer contour forming surface.

By tilting the slits, the effective volume of the slits on a plane parallel to the tread outer contour forming surface of the mold can be improved by comparing the slits having the same shape extending in the normal direction. It can be taken large and enhances the fluidity of air.

Further, the present invention according to claim 3 is the mold according to claim 1 or 2, wherein the inclination angle of the slit with respect to the normal to the tread outer contour forming surface is ± 20.
It is characterized by being in the range of ° to 40 °.

If the inclination angle exceeds ± 40 °, the slits are likely to be damaged when releasing the rubber vulcanized portion in the slit at the time of releasing from the mold, and further the block chip is likely to occur in the land portion in the vicinity. Is less than ± 20 °, the effective volume of the slit for enhancing the fluidity of air cannot be obtained sufficiently.

The present invention according to claim 4 is the mold according to any one of claims 1 to 3, wherein the shortest distance between the small hole and the tread outer contour forming surface is about 0.3 to 1.5 mm. It is characterized by being.

In order to form a narrow groove having a stable shape over the entire length of the blade opened on the surface of the tread when the tire is new, the small hole should be separated from the tread outer contour forming surface of the mold by 0.3 mm or more. Well, if the distance exceeds 1.5 mm, the flow of air will be hindered, and bears will easily occur due to air traps.

The present invention according to claim 5 provides the mold according to any one of claims 1 to 4, wherein the width t of the slit is t.
Is 0.2 to 0.7 mm, and the small hole is 1.0 to 1.5
It is characterized by being circular with a diameter d of mm.

If the diameter of the small hole is less than 1.0 mm, the flow of air will be hindered and the air bleeding effect will be reduced, and if it exceeds 1.5 mm, the dynamic performance of the product tire will be affected. If the slit width is less than 0.2, an effective volume that brings about air fluidity cannot be obtained, and if it exceeds 0.7 mm, the formation of the original narrow groove is hindered.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described with reference to FIGS. The blade 3 is planted in the tread forming portion of the tire of the mold 2 at the planting part 3B and fixed to the mold. The tread forming portion of the mold 2 is provided with a bone 6 forming a circumferential main groove and a bone 8 forming a lateral groove. Reference numeral 4 denotes a tread outer contour forming surface as viewed from the mold, which forms a land portion in the tread portion of the product tire together with various grooves formed by the circumferential main groove forming bone 6 and the lateral groove forming bone 8.

As shown in FIGS. 1 and 2, a small hole 11 having a width d is formed in the blade 3 of the present invention at a shortest distance S from the tread outer contour forming surface 4. The blade has a thickness of about 0.3 to 2.0 mm, and a relatively large volume air flow portion is formed in the vicinity of the tread outer contour forming surface 4 of the blade 3 by the small holes.

A slit 5 having a width t smaller than the width d from the small hole 11 is inclined at an angle of θ with respect to a normal line h to the tread outer contour forming surface 4 and is substantially linear inward of the mold. It extends and opens at the tip 3A of the blade. 7 is slit 5
The slit 5 is an opening to the blade tip 3A of
The small hole 11 and the opening 7 are communicated linearly. When the green tire is vulcanized by this mold, a cured rubber meat portion is formed in the slit 5, and the blade 3 is slid while leaving the rubber meat portion at the time of mold release.

The small hole 11 is formed near the tread outer contour forming surface 4 of the mold 2, and when viewed from a vulcanized product tire, the rubber meat portion formed by the small hole is a tread land when new. It will exist so as to connect both walls between the groove side walls in the narrow groove at a position that is lowered from the part surface to the inside of the tire.

The small hole 11 is, as in the following embodiment,
In addition to the circular shape, the shape may be an elliptical shape, a polygonal shape, or the like, and in any case, a relatively large volume air flow portion is formed in the blade.

The tire vulcanizing mold of the present invention is capable of sufficiently exerting the air bleeding function provided in the mold by using the blade that brings about such high air flowability.

[0028]

EXAMPLES In manufacturing a pneumatic tire of size 185 / 65R14 for passenger cars, a mold as shown in FIGS. 1 and 2 was used, in which the blade plate thickness was 0.7 mm and the small holes had a diameter of 1.0.
with a circular shape of 1.0 mm, a minimum separation distance S from the tread outer contour forming surface of the small-hole mold is 1.0 mm, and a slit width is 0.
Vulcanization was carried out by preparing 4 mm and the inclination angle θ of the slit at 25 °.

This mold has good air release during vulcanization of the tire, can prevent the occurrence of bareness due to air pockets and block breakage at the time of mold release, and is a high quality narrow grooved product tire. Was obtained, and the crack resistance was good even in the actual running of the tire.

[0030]

The tire vulcanizing mold of the present invention has a large number of blades for forming narrow grooves, but as described above, it has high air fluidity and suppresses the occurrence of bears. It is an excellent mold for tire vulcanization, which has good mold releasability and can vulcanize and cure high-quality narrow grooves on the tread portion of the tire.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a tire vulcanizing mold of the present invention.

FIG. 2 is a perspective view showing an embodiment of a tire vulcanizing mold of the present invention.

FIG. 3 is a schematic diagram illustrating a conventional tire vulcanizing mold and blade.

[Explanation of symbols]

2 Mold 4 Mold tread outer contour forming surface 6 Mold tread circumferential groove forming bone 8 Mold tread lateral groove forming bone 3 Blade 3A Blade tip 3B Blade implanting part 5 Slit 7 Opening 11 Small hole p Small hole diameter t Slit width S Smallest distance between small hole and mold tread outer contour forming surface h Normal to the tread outer contour forming surface of the die θ Slope angle to the normal h of the slit

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Claims (5)

[Claims] 1. A tire vulcanizing mold in which a large number of blades forming a narrow groove are planted in a tread portion of a tire,
The blade has a small hole provided in the vicinity of the tread outer contour forming surface of the mold, and a slit having a narrow width communicating from the small hole to the blade tip, and the width of the small hole is smaller than the width of the slit. A mold for tire vulcanization characterized by being large. 2. The tire vulcanizing mold according to claim 1, wherein the slit extends obliquely with respect to a normal line to the tread outer contour forming surface of the mold. 3. The tire vulcanizing mold according to claim 1, wherein an inclination angle of the slit with respect to a normal line to the tread outer contour forming surface is in a range of ± 20 to 40 °. 4. The tire vulcanizing metal according to claim 1, wherein a minimum distance S between the small hole and the tread outer contour forming surface is about 0.3 to 1.5 mm. Type. 5. The width t of the slit is 0.2 to 0.7 mm.
5. The tire vulcanizing mold according to claim 1, wherein the small hole has a circular shape having a diameter d of 1.0 to 1.5 mm.