JP2017213830A - Vulcanization mold of tire and manufacturing method of pneumatic tire using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inhibit cutout of a tread.SOLUTION: There is provided a vulcanization mold of a tire containing a tread molding face molding a tread part of the tire and a siping blade 13 for forming a sipe extending from the tread molding face to inside in a tire radius direction. The siping blade 13 has at least one open hole 15. The open hole 15 has a tilt at least in a mold radius direction with respect to a thickness direction while maintaining a cross section shape orthogonal to the thickness direction with the same shape.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a vulcanization mold for a tire having a sipe blade for forming a sipe and a method for manufacturing a pneumatic tire using the vulcanization mold for the tire.

  There is a pneumatic tire in which a plurality of sipes are formed on an outer surface of a tread portion. As a method for manufacturing such a pneumatic tire, for example, a vulcanization of a tire including a tread molding surface for molding the outer surface of the tread portion and a plurality of siping blades for forming a sipe provided on the tread molding surface. It is known to perform vulcanization molding using a mold.

  The vulcanization mold of a tire is provided with a vent hole that is a flow path for discharging air remaining between a tire before vulcanization molding and a tread molding surface during vulcanization. The siping blade is provided with a through hole that is a flow path for guiding the air sandwiched between adjacent siping blades to the vent hole.

  However, after the vulcanization molding, when the pneumatic tire is pulled out from the vulcanization mold, the rubber in the through hole is not cut in the through hole, and the surface of the siping blade, that is, the wall surface of the sipe is broken. There was a possibility that the tread chipping occurred. Related technologies include the following.

JP, 2014-151518, A

  The present invention has been devised in view of the above problems, and is based on improving the shape of the through hole provided in the siping blade, and when taking out a pneumatic tire from a vulcanization mold. The main object of the present invention is to provide a tire vulcanization mold and a method for producing a pneumatic tire that can produce a pneumatic tire in which the occurrence of tread chipping is suppressed.

  The present invention is a tire vulcanization mold including a tread molding surface for molding an outer surface of a tread portion of a tire, and a siping blade for forming a sipe extending inward in the tire radial direction from the tread molding surface. The siping blade is provided with at least one through-hole, and the through-hole maintains at least the mold in the thickness direction while maintaining the same cross-sectional shape orthogonal to the thickness direction. Inclined in the radial direction.

  In the tire vulcanization mold according to the present invention, the siping blade has a first surface and a second surface opposite to the first surface, and the through-hole is a first opening that opens at the first surface. And a second opening that opens on the second surface, and preferably extends linearly from the first opening to the second opening.

  In the tire vulcanization mold according to the present invention, it is preferable that the through hole has a positional deviation amount in the mold radial direction between the first opening and the second opening of 0.2 to 0.7 mm.

  The present invention is a method for producing a pneumatic tire, comprising a step of vulcanizing a pneumatic tire using the tire vulcanization mold according to any one of claims 1 to 3.

  The tire vulcanization mold of the present invention includes a tread molding surface for molding the outer surface of the tread portion of the tire, and a siping blade for forming a sipe extending inward in the tire radial direction from the tread molding surface. The siping blade is provided with at least one through hole. Thereby, the air sandwiched between adjacent siping blades is discharged from the vent hole, for example, through the through hole. For this reason, at the time of vulcanization, a bear formed by air collecting on the outer surface of the tire is suppressed.

  The through hole is inclined at least in the mold radial direction with respect to the thickness direction while maintaining the same cross-sectional shape orthogonal to the thickness direction. As a result, the siping blade is formed with an acute angle portion having an acute angle at both ends in the thickness direction in the cross-sectional shape passing through the through hole. Thus, when the tire is pulled out, a large shearing force acts in the radial direction of the mold on the rubber in the through hole, so that the rubber in the through hole is smoothly cut in the through hole. For this reason, generation | occurrence | production of a tread chip | tip etc. is suppressed. Moreover, since the through hole is maintained in the same shape in the cross-sectional shape orthogonal to the thickness direction, the smooth flow of air in the through hole is maintained. For this reason, a bear is suppressed reliably.

It is meridian sectional drawing which shows the vulcanization metal mold | die of this embodiment. It is a circumferential direction sectional view showing a tread forming ring. It is a perspective view of the segment of this embodiment. It is a perspective view of a siping blade. (A) is a cross-sectional view of the siping blade of the present embodiment, and (b) is a cross-sectional view of the siping blade of another embodiment. (A) is a cross-sectional view of a siping blade of a comparative example, and (b) is a cross-sectional view of a siping blade of another comparative example.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a cross-sectional view of a tire vulcanization mold (hereinafter sometimes simply referred to as “vulcanization mold”) 1 showing an embodiment of the present invention. The present invention is used, for example, in a vulcanization mold for manufacturing a pneumatic tire (hereinafter sometimes simply referred to as “tire”) T for a passenger car or a motorcycle.

  In the present embodiment, the tire T is provided with a plurality of grooves 21 extending in the tire circumferential direction and a notched sipe 22 extending in the tire axial direction on the tread portion Ta.

  The vulcanization mold 1 of this embodiment includes a tread molding ring 2 that molds the tread portion Ta of the tire T, a sidewall molding ring 3 that molds the sidewall portion Tb of the tire T, and a bead portion Tc of the tire T. A bead forming ring 4 to be formed is included. Further, the vulcanizing mold 1 includes a bladder B for vulcanizing and molding the inner cavity surface Td of the tire T.

  The bladder B is a bag-like body formed using, for example, a rubber composition or a synthetic resin. When the tire T is vulcanized and molded, for example, a high-temperature and high-pressure gas or liquid such as high-pressure steam is supplied to the bladder B to expand, and the unvulcanized tire is pressed against the vulcanization mold 1.

  As the sidewall molding ring 3 and the bead molding ring 4, those having a well-known structure are adopted, and each is formed of, for example, an annular body.

  As shown in FIG. 2, in the present embodiment, the tread molding ring 2 is formed as an annular body in which a plurality of segments 7 are connected in the tire circumferential direction. Each segment 7 can remove the tire T by moving radially outward as indicated by the phantom line.

  Each segment 7 of this embodiment has a tread molding surface 8, a pair of split surfaces 9, and a pair of side surfaces 10. The tread molding surface 8 molds the outer surface (shown in FIG. 1) Tm of the tread portion Ta. The dividing surfaces 9 extend outward in the mold radial direction from end edges 8e formed on both sides of the tread molding surface 8 in the tire circumferential direction. The side surfaces 10 extend outward in the mold radial direction from end edges 8i formed on both sides of the tread molding surface 8 in the tire axial direction.

  As shown in FIG. 3, the tread molding surface 8 of the present embodiment includes a reference surface 11, a circumferential bone portion 12, a siping blade 13, and a vent hole 14. The reference surface 11 forms a tread surface that contacts the road surface. The circumferential bone portion 12 forms a groove 21 of the tire T and extends from the reference surface 11 inward in the mold radial direction. The siping blade 13 forms a sipe 22 of the tire T and extends from the reference surface 11 inward in the mold radial direction. The vent hole 14 is, for example, a flow path extending from the tread molding surface 8 to the outside in the mold radial direction, and communicates with the reference surface 11 and the outside of the vulcanization mold 1. The number and arrangement positions of the vent holes 14 are variously determined depending on the shape of the tire T.

  In the present embodiment, the siping blade 13 is disposed between the circumferential bone portions 12 and 12 adjacent to each other in the mold axial direction, and between the circumferential bone portion 12 and the side surface 10 arranged on the outermost side in the mold axial direction. A plurality of each are provided.

  FIG. 4 is a cross-sectional view of the segment 7. As shown in FIG. 4, the siping blade 13 of the present embodiment extends linearly in the mold axis direction. Note that the siping blade 13 of the present invention is not limited to such a mode, and includes, for example, a zigzag mode and a wavy mode.

  The siping blade 13 has a first surface 13A and a second surface 13B on the opposite side. The first surface 13A of the present embodiment is a surface on one side (right side in FIG. 4) of the siping blade 13 in the thickness direction. Needless to say, the first surface 13A may be the surface on the other side in the thickness direction of the siping blade 13 (left side in FIG. 4).

  The siping blade 13 is provided with at least one through hole 15. Thereby, the air sandwiched between the adjacent siping blades 13 and 13 is discharged from the adjacent vent hole 14 through the through hole 15 during vulcanization. Thereby, since generation | occurrence | production of a bear is suppressed, the external appearance of the tire T is maintained highly.

  As shown in FIG. 5A, the through-hole 15 is inclined at least in the mold radial direction with respect to the thickness direction while maintaining the same cross-sectional shape orthogonal to the thickness direction. Thereby, the siping blade 13 is formed with acute angle portions 13c and 13c having acute angles at both ends in the thickness direction in the cross-sectional shape passing through the through hole 15. Thereby, for example, when the tire is pulled out, the rubber in the through hole 15 is smoothly cut in the radial direction of the mold, so that occurrence of tread chipping and the like is suppressed. Moreover, since the cross-sectional shape of the through-hole 15 is maintained at the same shape, air in the through-hole flows smoothly, so that bears are reliably suppressed.

  The through hole 15 of the present embodiment has a first opening 15a that opens at the first surface 13A and a second opening 15b that opens at the second surface 13B. In the present embodiment, the through hole 15 extends linearly from the first opening 15a to the second opening 15b. Such a through-hole 15 allows the air inside thereof to flow more smoothly, further suppressing bear.

  The through hole 15 preferably has a positional deviation amount L in the mold radial direction between the first opening 15a and the second opening 15b of 0.2 to 0.7 mm. When the positional deviation amount L is less than 0.2 mm, the shearing force of the acute angle portion 13 c becomes small, and the rubber may not be cut smoothly in the through hole 15. When the positional deviation amount L exceeds 0.7 mm, the air may not flow smoothly through the through hole 15. Further, when the positional deviation amount L exceeds 0.7 mm, the rigidity of the acute angle portion 13c is lowered, and the durability of the siping blade 13 may be deteriorated.

  In the present embodiment, the second opening 15b has a larger height in the mold radial direction from the reference surface 11 than the first opening 15a. The height h in the mold radial direction of the second opening 15b from the reference surface 11 is preferably about 0.5 to 1.0 mm.

  In the present embodiment, the through-hole 15 has a circular shape, but various forms such as a polygonal shape including a triangular shape and an elliptical shape are employed. Although not particularly limited, the inner diameter d of the through hole 15 is desirably about 0.5 to 3.0 mm.

  The thickness t of the siping blade 13 can take various values in accordance with the width (not shown) of the sipe 22, but is preferably about 0.3 to 2.0 mm, for example.

  FIG. 5B shows a through hole 15 of a siping blade 13 according to another embodiment of the present invention. In this embodiment, the through-hole 15 is linear from the first opening 15a and the second opening 15b toward the center in the thickness direction while maintaining the same cross-sectional shape in the mold radial direction. It is inclined to. Even in such a through-hole 15, tread chipping and the like are effectively suppressed. In this embodiment, it is desirable that the first opening 15a and the second opening 15b have the same height h in the mold radial direction from the reference surface 11.

  As shown in FIG. 1, the manufacturing method of the tire T using the vulcanizing mold 1 as described above is such that a green tire T1, which is a tire before vulcanization, is mounted in the vulcanizing mold 1 and the tire. A vulcanization step of pressurizing the lumen surface Td of T with a bladder B is provided. Since the manufacturing method and vulcanization method of the green tire T1 are the same as the conventional methods, the description thereof is omitted in this specification.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and can be implemented with various modifications.

  In order to confirm the effect of the present invention, a tire was manufactured using the vulcanization mold of FIG. And the appearance performance of the tread part of the manufactured tire was tested. The specifications of the vulcanization mold and the tire are common, including the tire internal structure and the manufacturing method, except for the specifications described in Table 1. The main common specifications are as follows.

<Siping blade>
Material: SUS304
Shape: Linear Width: 0.8mm
<Rubber composition of tire tread rubber>
The rubber used for the general passenger car tire which mix | blended silica etc. with the modified styrene butadiene rubber as a main component was used.
The test method is as follows.

<Appearance performance>
The presence or absence of tread chips near the bear and sipe in the tread portion of each sample tire was observed with the naked eye of the tester. As for the result of the bear and the tread chipping, the result that the aesthetic sense is ensured is passed, and the one that the aesthetic sense is impaired is shown as rejected. In addition, the internal diameter d of the through-hole of the comparative example 2 is the maximum diameter.
The test results are shown in Table 1.

  As a result of the test, the vulcanization molds of the examples have improved appearance performance because tread chipping and bears are suppressed as compared with the vulcanization molds of the comparative examples. In Example 2, it was found that the durability performance of the siping blade was slightly worse than that in Example 1. Further, in Example 5, it was found that tread chipping was slightly worse than that in Example 1. Furthermore, tests were performed on tires with different siping blade shapes, tread patterns, etc., and the same results as in Table 1 were shown.

DESCRIPTION OF SYMBOLS 1 Tire vulcanization mold 2 Tread molding surface 13 Siping blade 15 Through-hole T Tire Ta tread part

Claims (4)

A tire vulcanization mold including a tread molding surface for molding an outer surface of a tread portion of a tire, and a siping blade for forming a sipe extending inward in the tire radial direction from the tread molding surface,
The siping blade is provided with at least one through hole,
The tire vulcanization mold is characterized in that the through hole is inclined at least in the radial direction of the mold with respect to the thickness direction while maintaining the same cross-sectional shape orthogonal to the thickness direction. . The siping blade has a first surface and a second surface on the opposite side.
The said through-hole has the 1st opening opened on the said 1st surface, and the 2nd opening opened on the said 2nd surface, and has extended linearly from the said 1st opening to the said 2nd opening. 1. A tire vulcanization mold according to 1.   The tire vulcanization mold according to claim 2, wherein the through hole has a displacement amount of the first opening and the second opening in the mold radial direction of 0.2 to 0.7 mm.   A method for producing a pneumatic tire, comprising a step of vulcanizing a pneumatic tire using the tire vulcanization mold according to any one of claims 1 to 3.

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