JP6996280B2 - Tire vulcanization mold and tire manufacturing method - Google Patents

Description

The present invention relates to a vulcanization die for a tire and a method for manufacturing the tire, which suppresses the generation of bears in the sidewall portion.

It is known that when a tire is vulcanized and molded, an air pool is generated between the vulcanization die and the tire, and a bear (recessed portion) is formed on the outer surface of the tire. In particular, since marks such as letters and symbols are formed in an uneven shape on the sidewall portion of the tire, air is likely to collect and bears are likely to occur.

In order to prevent the occurrence of such a bear, it is known to provide a large number of vent holes for exhaust on the sidewall forming surface of the vulcanization die. However, if a large number of vent holes are arranged, the number of rubber protrusions called spews increases accordingly, which causes a problem that the aesthetic appearance of the tire is spoiled.

In recent years, it has been proposed to provide a narrow groove-shaped saw cut extending in the radial direction on the sidewall molded surface and use this as an air passage to improve the exhaust efficiency (see, for example, Patent Document 1).

However, in the case of saw cut, the formation position is subject to design restrictions such as the arrangement and size of the mark. Therefore, it may not be possible to continuously provide the saw cuts in the radial direction, or there may be places where the saw cuts themselves cannot be arranged, which impairs the degree of freedom in design and may not sufficiently suppress the generation of bears.

Japanese Unexamined Patent Publication No. 2014-76575

An object of the present invention is to provide a vulcanization die for a tire and a method for manufacturing the tire, which can suppress the generation of bears without being restricted by a design such as a mark.

The first invention of the present application is a vulcanization die for a tire including a side mold having a sidewall molding surface for molding the sidewall portion of the tire.
The contour shape of the sidewall molded surface changes in the tire circumferential direction,
Further, the contour shape includes a valley portion having a first contour line passing through the outermost side in the tire axial direction and a top having a second contour line passing through the innermost side in the tire axial direction among the contour lines in the tire meridional cross section. Form an uneven surface that is repeated alternately in the tire circumferential direction.

In the tire vulcanization die according to the present invention, the maximum value Dmax of the distance between the first contour line and the second contour line in the tire axial direction is 0.2 to 2.0 mm. preferable.

In the tire vulcanization die according to the present invention, the angle θ between the valley portion and the top portion about the tire axis is preferably 10 to 45 degrees.

In the tire vulcanization die according to the present invention, it is preferable that the valley portion and the top portion are repeated at equal intervals in the tire circumferential direction.

The second invention of the present invention is a method for manufacturing a tire, and includes a vulcanization step of vulcanizing a raw tire by the vulcanization mold of the tire of the first invention.

In the present invention, the contour shape of the sidewall molded surface is a valley portion having a first contour line passing through the outermost side in the tire axial direction and a second contour line passing through the innermost side in the tire axial direction among the contour lines in the tire meridional cross section. The top having the contour line of is formed into an uneven surface shape that is alternately repeated in the tire circumferential direction.

Therefore, during vulcanization molding, a space having a substantially triangular cross section with the valley as the apex is formed between the tire and the sidewall molding surface. This space extends continuously in and out of the radial direction. Therefore, this space functions as an exhaust passage, and the air between the tire and the sidewall molded surface can be exhausted to the outside.

Such a contour shape is not subject to design restrictions such as marks, or does not impose restrictions on the design. Therefore, it is possible to suppress the occurrence of bears while ensuring a wide degree of freedom in design.

It is a meridional cross-sectional view which shows one Embodiment of the vulcanization die of the tire of this invention. It is a perspective view of a side mold. It is a side view which looked at the sidewall molded surface from the inside in the tire axial direction. (A) is a partially developed view showing a tire circumferential cross section of a sidewall molded surface developed in a plane, and (B) is a drawing showing the action and effect of the present invention. (A) is a meridional cross-sectional view of a tire formed by the vulcanization die of the present invention, and (B) is a partial perspective view.

Hereinafter, embodiments of the present invention will be described in detail.
As shown in FIG. 1, the vulcanization die 1 of the tire of the present embodiment has a pair of side molds 2 for forming sidewalls and a tread mold 4 for forming treads arranged on both sides in the tire axial direction. A bead ring 5 for forming a bead is provided at the inner end of the side mold 2 in the radial direction of the tire. For convenience, FIG. 1 shows only one side of the tire equatorial plane Co in the tire axial direction.

In the vulcanization die 1, the butt surface S1 on the radial outer end side of the side mold 2 and the butt surface S2 on both sides of the tread mold 4 in the tire axial direction and on the radial inner end side are abutted against each other, and the side mold 2 The tire T is vulcanized in a mold closed state Y in which the butt surface S3 on the inner end side in the radial direction and the butt surface S4 on the outer end side in the radial direction of the bead ring 5 are butted against each other.

The side mold 2 includes a sidewall forming surface 2s for forming the sidewall portion of the tire T. The tread mold 4 includes a tread molding surface 4s for molding the tread portion of the tire T. The bead ring 5 includes a bead forming surface 5s for forming the bead portion of the tire T.

The same structure as the conventional one can be adopted as the tread mold 4 and the bead ring 5. Further, as the side mold 2, the same structure as the conventional one can be adopted except for the sidewall molded surface 2s. Therefore, the sidewall molded surface 2s will be mainly described below.

As shown in FIG. 2, the contour shape K of the sidewall molded surface 2s repeatedly changes in the tire circumferential direction. Specifically, the contour shape K has an uneven surface shape in which the valley portion 10 and the top portion 11 are alternately repeated in the tire circumferential direction. Of the contour lines J in the tire meridional cross section, the valley portion 10 has a first contour line Ja passing through the outermost side in the tire axial direction. Further, the top portion 11 has a second contour line Jb that passes through the innermost side in the tire axial direction among the contour lines J. The contour line J changes smoothly between the valley portion 10 and the top portion 11.

The "contour shape K" does not include partial fine irregularities composed of characters, symbols, figures and other marks generally formed on the sidewall molding surface 2s, and decorative patterns such as ridges.

As shown in FIG. 1, the maximum value Dmax of the distance D in the tire axial direction between the first contour line Ja and the second contour line Jb is preferably 0.2 to 2.0 mm. In this example, the maximum value Dmax appears as a distance D at the tire maximum width position Pm.

As shown in FIG. 3, the angle θ between the valley portion 10 and the top portion 11 about the tire axis i is preferably 10 to 45 degrees. In particular, it is preferable that the valley portion 10 and the top portion 11 are repeated at equal intervals in the tire circumferential direction. When the intervals are not equal, it is preferable that the maximum value and the minimum value of the angle θ are in the range of 10 to 45 degrees.

FIG. 4A is a partially developed view showing a cross section of the sidewall molded surface 2s in the tire circumferential direction developed in a plane. As shown in the figure, in this example, the valley portions 10 and 10 are formed by an arcuate curve 15 having a center on the outer side in the tire axial direction from the sidewall forming surface 2s and passing through the top portion 11. In this case, the sidewall forming surface 2s has an edge shape at the valley portion 10 and a smooth arc shape at the top portion 11. In the developed view, the sidewall forming surface 2s may be formed by a wavy curve such as a sine and cosine curve in which the valleys 10 and 10 form one cycle of the wave. As a result, the valley portion 10 and the top portion 11 can be made into a smooth curve.

In such a side mold 2, as shown in FIG. 4B, a space having a substantially triangular cross section with a valley portion 10 as an apex is provided between the tire T and the sidewall forming surface 2s during vulcanization molding. H is formed. This space H extends continuously in and out in the radial direction. Therefore, until the space H is filled with the rubber G due to the rubber flow during vulcanization, the space H functions as an exhaust passage, and the air between the tire T and the sidewall forming surface 2s is released in and out in the radial direction. Can be done. In this example, the escaped air is exhausted to the outside of the mold through the butt portion 20 between the side mold 2 and the tread mold 4 and the butt portion 21 between the side mold 2 and the bead ring 5, as shown in FIG. Can be made to.

If required, a vent hole can be formed at the position of the valley portion 10. Also in this case, since the air collects in the space H, the number of bent holes formed can be significantly reduced. The sidewall molded surface 2s having such a contour shape K is not subject to design restrictions such as marks, or is not restricted to the design. Therefore, it is possible to suppress the occurrence of bears while ensuring a wide degree of freedom in design.

Here, when the maximum value Dmax (shown in FIG. 1) of the distance D in the tire axial direction between the first and second contour lines Ja and Jb is less than 0.2 mm, the space H becomes too small and the exhaust passage. Will not work as well. On the contrary, when the maximum value Dmax exceeds 2.0 mm, the gauge thickness in the sidewall portion becomes non-uniform in the tire circumferential direction, and as a result, the lateral runout (LRO) deteriorates. From this point of view, the lower limit of the maximum value Dmax is preferably 0.5 mm or more, and the upper limit is preferably 1.5 mm or less.

Further, when the angle θ (shown in FIG. 3) between the valley portion 10 and the top portion 11 is less than 10 degrees, unevenness frequently appears in the tire circumferential direction, which causes deterioration of the appearance performance of the tire. On the contrary, when the angle θ exceeds 45 degrees, the space H (exhaust passage) interval becomes large, the exhaust becomes insufficient, and the effect of suppressing the occurrence of bears decreases. From this point of view, the lower limit of the angle θ is preferably 15 degrees or more, and the upper limit is preferably 30 degrees or less.

5 (A) and 5 (B) show the pneumatic tire T formed by the tire manufacturing method. This method for manufacturing a tire includes a vulcanization step of vulcanizing a raw tire with the vulcanization die 1.

Although the internal structure of the pneumatic tire T is omitted in FIGS. 5A and 5B, the same tire internal structure as the conventional one can be adopted. That is, for example, the carcass forming the skeleton of the tire, the belt layer arranged on the radial outside of the carcass and on the tread portion T1, the band layer arranged on the radial outside of the belt layer, the bead core arranged on the bead portion T2, and the like. It can be equipped with well-known components.

In the pneumatic tire T, the tire contour shape M on the outer surface of the sidewall portion T3 is repeatedly changed in the tire circumferential direction by being vulcanized and molded by the vulcanization die 1. Specifically, in the tire contour shape M, the valley portion 31 in which the contour line R in the tire meridional cross section passes through the innermost side in the tire axial direction and the top portion 32 in which the contour line R passes through the outermost side in the tire axial direction are in the tire circumferential direction. It forms an uneven surface that is repeated alternately. The maximum value Lmax of the distance L in the tire axial direction between the contour line in the valley portion 31 and the contour line in the top portion 32 is equal to the maximum value Dmax of the distance D in the vulcanization die 1.

Although the particularly preferred embodiment of the present invention has been described in detail above, the present invention is not limited to the illustrated embodiment and can be modified into various embodiments.

Passenger car tires with a tire size of 235 / 55R19 were vulcanized and molded using a vulcanization die having the specifications shown in Table 1. At that time, the bear occurrence situation and the tire lateral runout (LRO) were compared.

In the comparative example, 18 narrow groove-shaped saw cuts (groove width 0.5 to 1.0 mm, groove depth 0.5 to 1.0 mm) extending in the radial direction were formed on the sidewall molded surface in the tire circumferential direction. .. When the saw cuts are formed at 18 places at equal intervals, there are a plurality of places where the saw cuts interfere with the character design (mark). Therefore, in the comparative example, the position of the saw cut is shifted or a part of the saw cut is deleted in the interfering portion.

(1) Bear occurrence status:
1000 tires were manufactured and the appearance of the sidewall was visually inspected. Then, the generation rate (%) of the tire in which the bear caused by the air pool is generated was obtained as the bear generation rate. The smaller the value, the less the occurrence of bears, and the better the appearance quality.

(2) Lateral Runout (LRO):
Lateral runout (LRO) was measured for 1000 tires using a uniformity tester, and the average values were compared. The smaller the value, the smaller the lateral runout (LRO), and the better the uniformity.

As shown in the table, it can be confirmed that the examples can suppress the occurrence of bears while ensuring a wide degree of freedom in design.

1 Tire vulcanization die 2 Side mold 2s Side wall forming surface 10 Tani part 11 Top i Tire axis center J, Ja, Jb Contour line K Contour shape T Tire T3 Side wall part

Claims (6)

A vulcanization die for a tire that includes a side mold having a sidewall molding surface for molding the sidewall portion of the tire.
The contour shape of the sidewall molded surface changes in the tire circumferential direction,
Further, the contour shape includes a valley portion having a first contour line passing through the outermost side in the tire axial direction and a top having a second contour line passing through the innermost side in the tire axial direction among the contour lines in the tire meridional cross section. Form an uneven surface that repeats alternately in the tire circumferential direction ,
The vulcanization die of the tire includes a bead ring for forming a bead arranged at the inner end portion of the side mold in the radial direction of the tire.
At the time of vulcanization molding, the side mold is formed with a space having the valley as the apex between the side mold and the tire.
The space is a vulcanization die for a tire that extends continuously in and out in the radial direction and extends to a butt portion between the side mold and the bead ring. The vulcanization die includes a tread mold for forming a tread.
The vulcanization die for a tire according to claim 1 , wherein the space extends to a butt portion between the side mold and the tread mold . A vulcanization die for a tire that includes a side mold having a sidewall molding surface for molding the sidewall portion of the tire.
The contour shape of the sidewall molded surface changes in the tire circumferential direction,
Further, the contour shape includes a valley portion having a first contour line passing through the outermost side in the tire axial direction and a top having a second contour line passing through the innermost side in the tire axial direction among the contour lines in the tire meridional cross section. Form an uneven surface that repeats alternately in the tire circumferential direction,
A tire vulcanization die having an angle θ between the valley and the top centered on the tire axis of 10 to 45 degrees . The addition of the tire according to any one of claims 1 to 3, wherein the maximum value Dmax of the distance in the tire axial direction between the first contour line and the second contour line is 0.2 to 2.0 mm. Sulfur mold. The vulcanization die for a tire according to any one of claims 1 to 4, wherein the valley portion and the top portion are repeated at equal intervals in the tire circumferential direction. A method for manufacturing a tire, which comprises a vulcanization step of vulcanizing a raw tire using the tire vulcanization die according to any one of claims 1 to 5.

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