JP5836731B2 - Tire vulcanizing mold - Google Patents

Description

  The present invention relates to a tire vulcanization mold in which a vent hole is provided on a tire molding surface for molding an outer surface of a tire.

  Conventionally, in a tire vulcanization mold, a plurality of vent holes are provided on a tire molding surface for molding an outer surface of a tire. This vent hole leads to the inside and outside of the mold, and prevents the occurrence of dents called bears by discharging air between the outer surface of the tire and the tire molding surface during vulcanization molding It is.

  At the time of vulcanization molding, rubber on the outer surface of the tire flows into the vent hole, thereby forming a large number of rubber protrusions called spews. The spew is generally excised by trimming, but there are cases where the spew remains at a portion where trimming is difficult. Therefore, in order to improve the appearance of the tire, a cylindrical vent piece is inserted into the vent hole to form a thin and short spew (for example, Patent Document 1 below). A concave or convex portion is formed along the longitudinal direction on the inner peripheral surface of the vent piece of Patent Document 1, and index means that serves as an index of the degree of wear of the concave or convex portion is transferred to a spew at the time of tire molding. By displaying the display, it is possible to easily determine the degree of wear of the vent piece simply by observing the spew.

  By the way, when releasing the tire from the mold after vulcanization molding, the spew receives resistance due to contact with the vent hole or the inner peripheral surface of the vent piece, and the so-called spew cut may occur in the middle. is there. As a result, the vent hole or vent piece is clogged with spew, and air is not discharged during vulcanization molding, and bears are generated. In the vent piece of Patent Document 1, a concave portion or a convex portion is formed on the inner peripheral surface, and the contact area with the spew increases, so that the resistance at the time of pulling out increases and spew breakage is more likely to occur.

JP 2008-30402 A

  Accordingly, an object of the present invention is to provide a tire vulcanization mold capable of suppressing spew cutting by reducing the resistance that the spew receives from the inner surface of the vent hole or vent piece when releasing the tire from the mold after vulcanization molding. Is to provide.

The above object can be achieved by the present invention as described below.
That is, the tire vulcanization mold of the present invention is provided with a vent hole for discharging air between the outer surface of the tire and the tire molding surface at the time of vulcanization molding on the tire molding surface for molding the outer surface of the tire. In the tire vulcanization mold, a slit hole having a slit width of 0.03 mm or less is formed on the inner peripheral surface of the vent hole or the inner peripheral surface of the cylindrical vent piece fitted into the vent hole. It is characterized by that.

  A slit hole having a slit width of 0.03 mm or less is formed on the inner peripheral surface of the vent hole or the inner peripheral surface of the vent piece of the present invention. If it is a very small width of 0.03 mm or less, rubber does not enter the slit hole, air accumulates in the slit hole, and the slit hole portion does not contact the spew. Therefore, compared with a vent hole or a vent piece without a slit hole, the contact area with the spew can be reduced, so that the resistance that the spew receives from the inner peripheral surface of the vent hole or the vent piece can be reduced, and spew cutting can be suppressed.

  In the tire vulcanization mold according to the present invention, it is preferable that the depth direction of the slit hole forms an acute angle with the air discharge direction. The spew is formed in the air discharge direction, and when the tire is released from the mold after vulcanization molding, the spew is pulled out in the direction opposite to the air discharge direction. According to the present invention, the pulling direction of the spew makes an obtuse angle with the depth direction of the slit hole, so that the pulling resistance that the spew receives from the opening of the slit hole when pulling out can be reduced, and spew breakage can be further suppressed.

  In the tire vulcanization mold according to the present invention, it is preferable that a plurality of the slit holes are arranged along the circumferential direction of the inner peripheral surface of the vent hole or the vent piece. According to this configuration, the contact area in the circumferential direction with the spew can be effectively reduced by the slit hole, so that spew cutting can be further suppressed.

  In the tire vulcanization mold according to the present invention, it is preferable that the slit holes are arranged in a spiral shape. According to this configuration, the resistance that the spew receives due to the contact with the inner surface of the vent hole or the vent piece changes in the circumferential direction due to the difference in the distance from the air inlet to the slit hole. For this reason, peeling between the spew and the vent hole or the inner peripheral surface of the vent piece gradually occurs in the circumferential direction, so that an unreasonable force is not applied to the spew, and spew cutting can be further suppressed.

  In the tire vulcanization mold of the present invention, it is preferable that the length direction of the slit hole is inclined in the air discharge direction. According to this configuration, the pulling direction of the spew is inclined in the length direction of the slit hole, and compared to the parallel case, the contact area in the circumferential direction with the spew can be effectively reduced by the slit hole. Spew cutting can be further suppressed.

1 is a longitudinal sectional view schematically showing an example of a tire vulcanizing mold according to the present invention. Sectional drawing which expands and shows the vent hole provided in the tire molding surface (A) Front view and side view of vent piece, (b) Development view of inner peripheral surface (A) Front view and side view showing another example of vent piece, (b) Development of inner peripheral surface (A) Front view and side view showing another example of vent piece, (b) Development of inner peripheral surface (A) Front view and side view showing another example of vent piece, (b) Development of inner peripheral surface

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a longitudinal sectional view schematically showing an example of a tire vulcanization mold according to the present invention. The tire vulcanization mold (hereinafter may be simply referred to as a mold) of the present embodiment includes a tread mold part 1 that abuts on a tread part of the tire, a side mold part 2 that abuts on a sidewall part of the tire, and the like. 3 and a bead ring 4 to which a bead portion of a tire is fitted.

  At the time of vulcanization molding, the mold is opened by an unillustrated opening / closing mechanism, the green tire is set so that the tire axial direction is up and down, the mold is clamped, and a rubber bag called a bladder is inflated to expand the green tire. Extended deformation. Thereby, the outer surface of the green tire is pressed against the tire molding surface 1a.

  Although not shown, the tire molding surface 1a is provided with a bone portion (convex portion) for forming a groove portion and a concave portion for forming a land portion. A tread pattern corresponding to the shape is formed on the tread surface of the tire. The tire molding surface 1a is provided with a number of vent holes leading to the outside of the mold, and is configured to be able to discharge air between the outer surface of the tire and the tire molding surface 1a to the outside. Usually, a vent hole is provided in each of the recesses.

  FIG. 2 is an enlarged cross-sectional view showing a vent hole provided in the tire molding surface 1a. A cylindrical vent piece 6 having a vent hole 7 is fitted into the vent hole 5. Here, the air discharge direction ED is from right to left in FIG.

  FIG. 3A is a front view showing the appearance of the vent piece 6 and a side view thereof. FIG. 3B is a development view in which the inner peripheral surface of the vent piece 6 is developed. In the vent piece 6, slits 8 are respectively formed from the upper and lower sides of the outer peripheral surface 6a toward the inside. The slit 8 is formed by wire cut electric discharge machining, laser cut machining, or cutting using an end mill. The slit 8 is formed so as to reach the inner peripheral surface 6b, and by inserting the vent piece 6 into the vent hole 5, the outer peripheral surface 6a of the vent piece 6 is closed. A slit hole 9 is formed in the peripheral surface 6b from the inner peripheral surface 6b to the outside.

  The slit hole 9 has an elongated slit-shaped opening 9a that opens to the inner peripheral surface 6b. A direction from the slit-shaped opening 9 a toward the outer peripheral surface 6 a is a depth direction DD of the slit hole 9. Further, when viewed in the depth direction DD, the longitudinal direction of the slit-shaped opening 9 a is defined as the length direction LD of the slit hole 9, and the short direction of the slit-shaped opening 9 a is defined as the width direction WD of the slit hole 9.

  The slit width W of the slit hole 9 is 0.03 mm or less, preferably 0.02 mm or less. If the slit width W is 0.03 mm or less, almost no rubber enters the slit hole 9 during vulcanization molding, and instead air accumulates in the slit hole 9 and the slit hole 9 does not contact the spew.

  In the present embodiment, the depth direction DD of the slit hole 9 is perpendicular to the air discharge direction ED.

  A plurality of slit holes 9 are arranged along the circumferential direction of the inner peripheral surface 6 b of the vent piece 6. The circumferential direction of the inner peripheral surface 6b is the vertical direction of FIG. Here, an example is shown in which two opposing slit holes 9 are formed at the same position in the air discharge direction ED. Two opposing slit holes 9 are formed in pairs along the discharge direction ED.

  The slit hole 9 is preferably formed within a range of at least 15 mm from the tire molding surface 1a toward the air discharge direction ED. This is because the length of the spew formed by the rubber flowing into the vent piece 6 is set to be approximately 15 mm or less.

  The tire vulcanization mold of the present invention is the same as a normal tire vulcanization mold except that the vent piece is configured as described above, and any conventionally known shape, material, opening / closing mechanism, etc. It can be employed in the invention. In the above-described embodiment, a mold structure having a tread mold part and a pair of side mold parts has been shown. However, in the present invention, a mold that has a dividing surface at the center part of the tread mold part and is divided into two parts up and down. A mold structure may be used.

<Another embodiment>
(1) In the above-described embodiment, the depth direction DD of the slit hole 9 is perpendicular to the air discharge direction ED. However, as shown in FIG. 4, the slit hole 9 has an acute angle with the air discharge direction ED. Is preferred. The angle α formed by the depth direction DD and the discharge direction ED is preferably 10 to 60 °.

  (2) As shown in FIG. 5, the slit holes 9 are preferably arranged in a spiral shape. FIG. 5 shows an example in which the depth direction DD of the slit hole 9 forms an acute angle with the air discharge direction ED, and the slit holes 9 are arranged in a spiral shape. In this example, slits 8 are formed from three directions with respect to the outer peripheral surface 6 a of the vent piece 6.

  (3) In the above-described embodiment, the length direction LD of the slit hole 9 is perpendicular to the air discharge direction ED, but may be parallel to the air discharge direction ED. However, the length direction LD of the slit hole 9 is preferably inclined in the air discharge direction ED. FIG. 6 shows an example in which the slit holes 9 are arranged in a spiral and the length direction LD of the slit holes 9 is inclined in the air discharge direction ED.

  (4) In all the embodiments described above, the slit hole 9 is formed on the inner peripheral surface of the vent piece 6, but the slit hole may be formed on the inner peripheral surface of the vent hole 5. In this case, a slit hole is formed from the inner peripheral surface of the vent hole 5 to the outside. However, since it is difficult to form a minute slit hole from the inner peripheral surface, the vent piece 6 is considered in consideration of the workability of the slit hole. It is more preferable to form a slit hole in the inner peripheral surface.

  In order to specifically show the configuration and effects of the present invention, the tire was vulcanized and examined for spout breakage. A comparative example is one in which no slit hole is formed on the inner peripheral surface of the vent piece. Example 1 in which the slit hole shown in FIG. 3 is formed in the vent piece of the comparative example, Example 2 in which the slit hole shown in FIG. 4 is formed, and Example 2 in which the slit hole shown in FIG. 5 is formed 3, what formed the slit hole shown in FIG. The inner diameter of the inner peripheral surface was 0.65 mm, and the slit width was 0.02 mm. In each example, the presence or absence of spew out of 100 tires was examined, and each good product ratio when the good product ratio in Comparative Example 1 was taken as 100 was expressed as an index. The larger this value, the less spew breakage occurred. The evaluation results are shown in Table 1.

  As shown in Table 1, in each example, spout breakage is less generated than in the comparative example, and spew breakage can be suppressed.

DESCRIPTION OF SYMBOLS 1 Tread type part 1a Tire molding surface 5 Vent hole 6 Vent piece 6a Outer peripheral surface 6b Inner peripheral surface 7 Vent hole 8 Slit 9 Slit hole 9a Slit-shaped opening

Claims (5)

In the tire vulcanization mold provided with a vent hole for discharging air between the outer surface of the tire and the tire molding surface during vulcanization molding on the tire molding surface for molding the outer surface of the tire ,
The inner peripheral surface of the tubular vent piece is fitted before Symbol vent hole, a tire vulcanizing mold, wherein a slit hole below the slit width 0.03mm is formed.   The tire vulcanization mold according to claim 1, wherein a depth direction of the slit hole forms an acute angle with an air discharge direction. The slit holes, a tire vulcanizing mold according to claim 1 or 2, characterized in that it is arrayed along the circumferential direction of the inner peripheral surface of the front Kibe Ntopisu.   The tire vulcanization mold according to claim 3, wherein the slit holes are arranged in a spiral shape.   The tire vulcanization mold according to any one of claims 1 to 4, wherein a length direction of the slit hole is inclined in an air discharge direction.

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