JP2008273084A - Tire vulcanization mold and pneumatic tire vulcanized by the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress poor appearance due to the occurrence of air traps during vulcanization when manufacturing a pneumatic tire having a rim guard. <P>SOLUTION: A large number of ridges extending in a tire meridional direction are provided on the side face 9 of a rim guard 7 of a pneumatic tire 1. A large number of ridges extending in a tire meridional direction and one ridge extending in a tire circumferential direction are provided on the tip face (the top) 8 of the rim guard 7. A recessed part 22a corresponding to the rim guard 7 is provided in the inner face of a side mold 22. Grooves corresponding to the ridges are provided in the side face 22b and the bottom face 22c of the recessed part. The grooves accelerate the rubber flow to the recessed part 22a during vulcanization. Accordingly, air in the recessed part 22a escapes through a vent hole 22d in the bottom face 22c. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a tire vulcanization mold and a pneumatic tire vulcanized thereby, and more specifically, an appearance caused by the occurrence of air pockets during vulcanization when manufacturing a pneumatic tire having a rim guard. The present invention relates to a tire vulcanization mold capable of suppressing defects and a pneumatic tire vulcanized thereby.

  The flattening of tires has progressed with the times, and tires with a flatness ratio of about 60% were previously called flat tires, but recently, tires with a flatness ratio of 45% or 40% have also appeared.

  When tires are flattened, the section height (cross-sectional height) becomes relatively low, which improves the responsiveness of the vehicle when the steering wheel is turned and the operability is greatly improved. Can be mentioned. For this reason, tires with such a low section height are mounted mainly on sports cars.

  However, there is a disadvantage in reducing the section height, and the deterioration of riding comfort and the damage of the tire side surface and rim flange are remarkable. The most common damage to the side surface is that the rubber on the side surface on the outer side in the tire axial direction is sandwiched between the rim flange and the curbstone, so that not only the rubber on that portion but also the carcass cord inside it can be cut. is there. As damage to the rim flange, there is a phenomenon in which the rim flange is damaged by contact with a curbstone or the like.

  In order to prevent such damage to the tire side surface portion and the rim flange, as shown in FIG. 4, a rim guard 7 made of a protrusion continuous in the tire circumferential direction is provided on the outer surface (outer surface in the tire axial direction) of the bead portion 4. It is known (see Patent Document 1). Thus, by providing the rim guard 7 made of an annular protrusion on the outer surface of the bead portion 4, damage to the outer surface of the bead portion 4 or the carcass cord of the carcass ply 6 in the bead portion 4 can be suppressed. Further, by causing the rim guard 7 to sufficiently protrude from the outer surface of the bead portion 4, damage to the rim flange Rf can be suppressed. The rim guard 7 is employed in many flat tires because it has not only such a practical effect but also an effect of improving the appearance such that the tire side surface is tightened.

  As the protrusion length of the rim guard 7 is longer, the above-described effect becomes greater. Further, in order to cover the rim flange Rf and prevent its damage, a protrusion length (height) of at least about 6 mm is required.

  By the way, in order to provide a protrusion on the outer surface of the tire, a concave portion corresponding to the protrusion is required on the inner surface of the tire vulcanizing mold. Therefore, when manufacturing a pneumatic tire having a rim guard with a protruding length of 6 mm or more, a bead is used. It is necessary to vulcanize with a mold having a recess having a depth of 6 mm or more in the part to be molded.

  However, when an unvulcanized tire is vulcanized with a mold having a recess having a depth of 6 mm or more, due to the problem of rubber fluidity, the outer surface of the bead portion of the unvulcanized tire and the recess corresponding to the rim guard The air in between may not escape and an air pocket may occur. As a result, an appearance defect occurs due to a rough surface called a bear occurring on the surface of the rim guard of the vulcanized tire. Recently, there are increasing opportunities to manufacture extremely flat tires having a flatness ratio of 35% or 30%. Therefore, it is a major issue at the manufacturing site to suppress this appearance defect.

JP-A-8-282218

  The present invention has been made in view of the above-described conventional problems, and its object is to suppress appearance defects caused by the occurrence of air pockets during vulcanization when manufacturing a pneumatic tire having a rim guard. It is.

The invention according to claim 1 vulcanizes and molds a pneumatic tire having a tread portion and a pair of sidewall portions and bead portions continuous on both sides of the tread portion, and at least one of the bead portions includes a rim guard protruding to the outside of the tire. In the tire vulcanization mold for the above, a recess corresponding to the rim guard is provided on the inner surface, and a plurality of grooves extending in a direction intersecting the tire circumferential direction are provided on a side surface of the recess, A plurality of grooves extending in a direction crossing the tire circumferential direction and one or more grooves extending in the tire circumferential direction are provided.
According to a second aspect of the present invention, in the tire vulcanization mold according to the first aspect, a direction intersecting the tire circumferential direction is a tire meridian direction.
According to a third aspect of the present invention, in the tire vulcanization mold according to the first or second aspect, the depth of the groove is 0.2 mm or more and 2.0 mm or less.
According to a fourth aspect of the present invention, in the tire vulcanization mold according to any one of the first to third aspects, a vent hole is provided on a bottom surface of the groove extending in the tire circumferential direction.
A fifth aspect of the present invention is a pneumatic tire characterized by being vulcanized by the tire vulcanization mold according to any one of the first to fourth aspects.

(Function)
According to the invention of claims 1 to 3, the rubber outside the bead portion of at least one of the unvulcanized tires arranged inside the mold is provided on the side surface of the recess for forming the rim guard. By flowing along a groove extending in a direction intersecting the tire circumferential direction, the flow of rubber with respect to the recess is promoted. The rubber that has reached the bottom surface of the recess first flows along a groove extending in a direction intersecting with the tire circumferential direction, and flows in the tire circumferential direction along the groove extending from the intersection with the groove extending in the tire circumferential direction. Therefore, the rubber flow at the bottom of the recess is promoted.
According to invention of Claim 4, the air between the outer surface of the bead part of an unvulcanized tire and the recessed part for forming a rim guard escapes from the vent hole of the bottom face of the 2nd groove | channel of the recessed part bottom face. Go.

  According to the present invention, since it is possible to reduce the occurrence of air accumulation between the outer surface of the bead portion of the unvulcanized tire and the recess for forming the rim guard, appearance defects due to the occurrence of air accumulation are reduced. Can be suppressed.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a perspective view showing a schematic configuration of a pneumatic tire vulcanized by a tire vulcanization mold according to an embodiment of the present invention. In this figure, the same or corresponding parts as those in FIG. Further, only one side with respect to the tire equator is shown here, but the other side of the figure with respect to the tire equator is similarly configured except for the rim guard 7.

  The pneumatic tire 1 of the present embodiment includes a tread portion 2, a pair of sidewall portions 3 that are continuous with both sides of the tread portion 2, and a pair of bead portions 4 that are continuous with the sidewall portion 3. A bead core 5 is provided inside the bead portion 4, and a carcass ply 6 is provided between the pair of bead cores 5 so as to straddle a toroidal shape. The end portion of the carcass ply 6 is formed so as to be folded back from the inner side in the tire axial direction of the bead core 5. Further, a rim guard 7 which is an annular protrusion continuous in the tire circumferential direction is provided on the tire outer surface of the bead portion 4. In the present embodiment, the rim guard 7 is provided only on the side of the pair of bead portions 4 that faces the outside of the vehicle body when attached to the wheel, but may be provided on both of the pair of bead portions 4. Here, the tire meridian cross-sectional shape of the rim guard 7 is substantially trapezoidal, but it may be substantially triangular.

  A plurality of ridges 10, 12 extending in the direction perpendicular to the tire meridian direction, that is, the tire circumferential direction (tire equator direction), are provided at equal intervals on the protruding end surface (top of the protrusion) 8 and the side surface 9 of the rim guard 7. Although not shown, the rim guard 7 has a protruding end surface 8 provided with a single ridge extending in the tire circumferential direction.

  The detailed shape of the rim guard 7 in FIG. 1 is shown in FIG. Here, A is a tire meridian sectional view of the rim guard 7 (viewed from the direction of arrow X in FIG. 1), and B is a view of the protruding end of the rim guard 7 from the outside (viewed from the direction of arrow Y in FIG. 1). C) is a view of the rim guard 7 as seen from the tire meridian direction (the direction of arrow Z in FIG. 1). Here, one ridge 11 provided on the protruding end face 8 is shown.

  As shown in these figures, the cross-sectional shapes of the ridges 10 to 12 are isosceles triangles. The heights h1, h2, and h3 of the ridges 10, 11, and 12 are distances between the vertices 10a, 11a, and 12a of the isosceles triangles and the bases 10b, 11b, and 12b, respectively.

  FIG. 3 is a meridian cross-sectional view on the right side of the tire equator CL of each of the pneumatic tire 1 and the vulcanizing mold 20 for manufacturing the pneumatic tire 1 shown in FIG. The tire vulcanizing mold 20 is called a split mold, and includes a plurality of arc-shaped segment molds 21 for forming the tread portion 2 of the pneumatic tire 1, the sidewall portions 3 and the bead portions 4. And an annular side mold 22 for forming. The left side of the tire equator CL of the vulcanizing mold 20 is the same as the right side except that the configuration of the side mold 22 is partially different (there is no recess corresponding to the rim guard 7). Reference numeral 23 denotes a bead ring.

  As shown in FIG. 3, an annular recess 22 a corresponding to the rim guard 7 is provided on a part of the inner surface of the side mold 22 where the rim guard 7 of the pneumatic tire 1 is formed. The cross-sectional shape of the recess 22a is substantially trapezoidal as with the rim guard 7. Although not shown, a groove corresponding to the ridge 12 of the side surface 9 of the rim guard 7 is provided on the side surface 22b of the recess 22a, and the ridge of the protruding end surface 8 of the rim guard 7 is formed on the bottom surface 22c of the recess 22a. Grooves corresponding to 10 and 11 are provided. Further, an air venting vent hole 22d is provided on the bottom surface of the groove corresponding to the ridge 11.

  In order to manufacture the pneumatic tire shown in FIG. 1, when the raw tire is stored in the tire vulcanizing mold 20 shown in FIG. 3 and heated and pressurized from the inner surface, the rubber constituting the raw tire is obtained. The outer surface is pressed against the inner surfaces of the segment mold 21 and the side mold 22. Thereby, a part of rubber | gum of the outer surface of the bead part of a raw tire flows toward the recessed part 22a which opposes, and is accommodated in the recessed part 22a.

  At this time, the grooves formed in the side surface 22b and the bottom surface 22c of the recess 22a of the side mold 22 promote the flow of rubber. That is, when the rubber flows into the recess 22a, it flows along the side surface 22b, but a number of grooves formed in the side surface 22b extend in the tire meridian direction, that is, in the direction toward the bottom surface 22c of the recess 22a. Therefore, the flow of rubber toward the bottom surface 22c is promoted. The rubber that has reached the bottom surface 22c first flows along a groove extending in the tire meridian direction, and flows in the tire circumferential direction along the groove from the intersection with the groove extending in the tire circumferential direction. . At this time, the air staying in the recess 22a can escape to the outside of the mold through the vent hole 22d for releasing air formed in the bottom surface 22c.

  Thus, according to the tire vulcanization mold of the present embodiment, the flow of the unvulcanized rubber is caused by the grooves provided in the side surface 22b and the bottom surface 22c of the recess 22a for forming the rim guard on the inner surface of the side mold 22. In addition to being promoted, the vent hole 22d provided in the bottom surface 22c efficiently exhausts the recess 22a, so that the occurrence of air pockets can be reduced as compared with the prior art. Thereby, appearance defects, such as the bear of the surface of the rim guard 7 resulting from generation | occurrence | production of an air pocket, can be reduced.

  Here, the depth of the groove formed in the side surface 22b of the recess 22a, the groove formed in the tire meridian direction and the groove extending in the tire circumferential direction formed in the bottom surface 22c is 0.2 mm or more and 2.0 mm or less. It is preferable. When the depth is less than 0.2 mm, the effect of promoting the flow of rubber becomes slight. When the depth is deeper than 2.0 mm, the height of the ridges 10 to 12 of the rim guard 7 exceeds 2.0 mm correspondingly. This is because it causes a decline in sex. Accordingly, the preferable values of the heights h1, h2, and h3 of the ridges 10, 11, and 12 formed by these grooves are 0.2 mm or more and 2.0 mm or less, which is the same as the depth of the grooves.

  In the above description, the groove formed on the side surface 22b of the recess 22a corresponding to the ridge 12 and the groove formed on the bottom surface 22c corresponding to the ridge 10 are orthogonal to the tire meridian direction, that is, the tire circumferential direction. However, it is only necessary to intersect even if they are not orthogonal. In other words, the grooves may be formed so that the ridges 10 and 12 shown in FIG. 2 extend in the direction intersecting the tire circumferential direction. The heights of the multiple ridges 10 and the heights of the multiple ridges 12 may not be the same. Further, the number of grooves formed in the bottom surface 22c corresponding to the ridge 11 may be two or more, in other words, the ridge 11 shown in FIG. 2 may be two or more. About vent hole 22d, it is preferable to exhaust evenly by providing two or more at equal intervals in the tire peripheral direction.

[Example]
In order to confirm the effect of the present invention, the conventional tire (FIG. 4) and the mold for vulcanizing and molding the tire of the present embodiment (FIGS. 1 and 2) and the mold for vulcanizing and molding the tire respectively (FIG. 4) Table 1 shows the results of making 400 prototypes of each and comparing the incidence of appearance defects. Here, the tire size is 245 / 45R17 for both the conventional tire and the example tire. In the embodiment, the heights of the ridges 10, 11, and 12 are all 0.4 mm. The ridges 10 and 12 were extended in the tire meridian direction and arranged at a density of 20 per 10 mm. One ridge 11 is provided on the protruding end surface 8 of the rim guard 7. Six vent holes 22d are provided at equal intervals in the circumferential direction on the bottom surface of the groove corresponding to the ridge 11.

  From this table, it can be confirmed that the effect of the present invention is extremely large in the example, because the appearance defect occurrence rate of the surface of the rim guard 7 is reduced from 7500 PPM of the conventional example to 1/3 2500 PPM.

1 is a perspective view showing a schematic configuration of a pneumatic tire vulcanized by a tire vulcanization mold according to an embodiment of the present invention. It is a figure which shows the detailed shape of the rim guard in FIG. FIG. 2 is a meridian cross-sectional view on the right side of the tire equator CL of each of the pneumatic tire shown in FIG. 1 and a vulcanization mold for manufacturing the pneumatic tire. It is meridian sectional drawing of the principal part of the conventional pneumatic tire which has a rim guard.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Pneumatic tire, 2 ... Tread part, 3 ... Side wall part, 4 ... Bead part, 7 ... Rim guard 10, 11, 12 ... Ridge, 20 ... Tire vulcanization mold, 22 ... side mold, 22a ... recess, 22b ... side surface of recess, 22c ... bottom surface of recess, 22d ... vent hole.

Claims (5)

Tire vulcanization gold for vulcanizing and molding a pneumatic tire having a tread portion and a pair of sidewall portions and bead portions continuous on both sides thereof, and at least one of the bead portions includes a rim guard protruding outward from the tire. In the mold,
A plurality of grooves extending in a direction intersecting the tire circumferential direction are provided on a side surface of the recess, and a plurality of grooves extending in a direction intersecting the tire circumferential direction are provided on a bottom surface of the recess. The tire vulcanization mold is provided with at least one groove and one or more grooves extending in the tire circumferential direction. The tire vulcanization mold according to claim 1,
A tire vulcanization mold, wherein a direction intersecting with the tire circumferential direction is a tire meridian direction. In the tire vulcanization mold according to claim 1 or 2,
A tire vulcanization mold, wherein the groove has a depth of 0.2 mm to 2.0 mm. In the tire vulcanization mold according to any one of claims 1 to 3,
A tire vulcanization mold, wherein a vent hole is provided in a bottom surface of a groove extending in the tire circumferential direction.   A pneumatic tire characterized by being vulcanized by the tire vulcanization mold according to any one of claims 1 to 4.

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