JPH08216154A - Preparation of pneumatic radial tire and bladder used for the preparation - Google Patents

Abstract

PURPOSE: To vulcanize and mold with good accuracy a tire in which the carcass of the tire is complicatedly deviated to both the inside and the outside. CONSTITUTION: At least one projected part 11 and at least one recessed part 12 are provided on the inner face part of a corresponding mold 2 between the neighborhood of the shoulder part 10 and the bead part 4 of a tire to be prepd. On the other hand, a recessed part 13 and a projected part 14 each with an approximately similar figure to the projected part 11 and the recessed part 12 are provided on the outside face of the bladder 3 of the parts each corresponding to the projected part 11 and the recessed part 12 provided on the inner face of this mold 2 and an inner pressure is filled into the bladder 3 in the mold 2 to bring it into contact with the inner face of a green tire 1 and while in the inner face side of the bladder, a natural equilibrium shape is kept, the green tire 1 is vulcanized and molded. The carcass 5 part is deviated thereby by the projected part and the recessed part to both inside and outside of the tire from the natural equilibrium shape.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a pneumatic radial tire and a bladder used therefor, and more particularly to a method for accurately forming a complicated carcass shape on a tire side portion.

[0002]

2. Description of the Related Art Conventionally, tires are manufactured by using a bladder whose thickness changes almost uniformly or smoothly. Further, as a tire manufacturing method and a bladder used for the tire having a complicated carcass shape on the tire side,
There is a technique as described in Japanese Patent Application Laid-Open No. 5-417 by the present applicant.

[0003]

However, when a tire is manufactured with a mold having protrusions and depressions on the inner surface using a bladder whose thickness changes almost uniformly or smoothly, the bladder naturally balances. It approaches the shape and interferes with the formation of a tire with a complicated carcass shape on the tire side. Further, in the technique described in the above publication, the carcass portion of the tire is displaced only from the natural equilibrium shape of the tire to the inside of the tire by the protrusion provided on the inner surface of the mold. Then, in order to make such a tire, a bladder in which the expansion rate of the portion corresponding to the protrusion provided on the inner surface of the mold is partially lowered is inscribed in the green tire and vulcanized and molded in the mold. I am trying to obtain a good desired tire. However, in order to manufacture a tire in which both the protrusion and the depression are provided on the inner surface of the mold and the carcass part is complicatedly displaced from the natural equilibrium shape to both the inside and the outside of the tire, as described above. A bladder with a partially reduced expansion rate is not sufficient. In particular, in order to sufficiently press the green tire into the recess on the inner surface of the mold where the carcass part is offset to the outside of the tire, the conventional bladder is insufficiently inscribed and a precise shape cannot be obtained. There is a problem.

Therefore, in consideration of such a problem, an object of the present invention is to accurately and accurately vulcanize a tire in which the carcass portion of the tire is complicatedly displaced from the natural equilibrium shape to both the inside and the outside of the tire. It is intended to provide a method for producing a pneumatic radial tire that can be molded and a bladder used for the method.

[0005]

According to the method of manufacturing a pneumatic radial tire of the present invention, a side end portion of at least one cord ply of a carcass composed of cord plies of a toroidal radial arrangement straddling a pair of beads. Roll up from the tire inner side to the outer side around the bead core, the inner surface of the green tire configured by arranging the belt composed of a plurality of cord arrangement layers on the outer peripheral side of the crown portion of the carcass, and inscribe the bladder When manufacturing a pneumatic radial tire by vulcanizing and molding a green tire in a mold, in the mold inner surface part corresponding to the required position between the shoulder part and the bead part of the manufactured tire, from the mold inner surface The arc part with the center of curvature on the outer side and the inner and outer sides of this arc part in the radial direction of the mold are And at least one protrusion that extends inwardly of the mold and is divided by the respective arc portions that are smoothly centered on the arc portion and that is smoothly continuous to the arc portion, and that the manufacturing is performed as described above. In the mold inner surface portion corresponding to another required position between the vicinity of the shoulder portion and the bead portion of the tire, an arc portion having a center of curvature inside the inner surface of the mold and the inside and outside of the arc portion in the radial direction of the mold. Adjacent to the inner surface of the mold and the center of curvature is placed outside the inner surface of the mold, and the inner surface of the mold is dented by each arc portion that is smoothly continuous to the arc portion, and at least one dent portion that continuously extends in the mold circumferential direction is formed. On the other hand, on the other hand, on the outer surface of the bladder of the portion corresponding to the protrusion and the recess provided on the inner surface of the mold, the recess and the recess which are substantially similar to the protrusion and the recess are provided. By providing an internal pressure to the inner surface of the green tire by filling the bladder with internal pressure in the mold, the inner surface side of the bladder is vulcanized and molded while maintaining a natural equilibrium shape, thereby forming a carcass part. The protrusions and the recesses cause the natural equilibrium shape to be displaced both inward and outward of the tire.

According to the second aspect of the present invention, the bladder has a mold inner surface portion corresponding to a desired position between the vicinity of the shoulder portion and the vicinity of the bead portion of the tire to be manufactured, which is outside the mold inner surface. And a circular arc portion having a center of curvature as the center of curvature and a circular arc portion adjacent to the inside and outside of the circular arc portion in the mold radial direction and having a center of curvature inside the inner surface of the mold and smoothly continuing to the circular arc portion. A mold corresponding to another required position between the vicinity of the shoulder portion and the vicinity of the bead portion of the tire to be manufactured, which is provided with at least one protrusion protruding inward and continuously extending in the mold circumferential direction. On the inner surface part, an arc part whose center of curvature is located inside the mold inner surface and a center of curvature adjacent to the inside and the outside of the arc part in the radial direction of the mold Can be partitioned depression mold inner surface with a respective arcuate portion smoothly continuous with the circular arc portion,
A bladder used for vulcanization molding of a tire together with a mold having at least one recess extending continuously in the mold circumferential direction, the bladder being a portion corresponding to each of the protrusion and the recess on the inner surface of the mold. The outer surface is formed with recesses and protrusions that are similar in shape to the protrusions and recesses by changing the thickness of the bladder.

[0007]

According to the manufacturing method and the bladder of the present invention, the mold inner surface portion corresponding to the required position between the vicinity of the shoulder portion and the vicinity of the bead portion of the tire to be manufactured, and the mold inner surface portion corresponding to another required position, respectively. Has a protrusion protruding inward from the natural equilibrium shape and a recess depressed outward from the natural equilibrium shape. Further, substantially similar recesses and projections are formed on the outer surface of the bladder corresponding to the projections and recesses provided on the inner surface of the mold. The protrusion and the recess formed on the outer surface of the bladder are formed by increasing and decreasing the thickness of the bladder, respectively. Therefore, in the state where the bladder is not filled with the pressurized fluid, the inner surface of the bladder does not have the protrusion and the recess corresponding to the outer surface, but has a gentle surface.

Therefore, when the bladder is filled with the pressurized fluid in the mold and inscribed in the green tire to be vulcanized and molded, the thickness formed on the outer surface of the bladder at the initial stage of the inscribement of the green tire and the bladder. The thick protrusion of the first part is inscribed in the green tire first, and the carcass part of the green tire is strongly displaced toward the concave part of the inner surface of the mold. Then, the green tire and the recessed portion of the outer surface of the bladder are inscribed in the end at the latest, and finally, the inner surface of the green tire and the outer surface of the bladder are inscribed uniformly over the entire surface. At this time, since the inner surface side of the bladder is a smooth curved surface that is relatively uneven and has a natural equilibrium shape of the tire, the pressure of the pressurized fluid exerts almost no force on the bladder outer surface to press the green tire against the inner surface of the mold. Be uniform. However, since the protrusions and depressions are formed on the outer surface of the bladder by changing the wall thickness of the bladder,
The inner surface of the green tire has a shape that is displaced inward and outward along the protrusions and depressions on the outer surface of the bladder.

Here, the thin rubber layer called the inner liner, which is the outer skin on the inner surface side of the green tire, is made of a material that does not allow air to easily pass through so that the internal pressure of the tire does not leak to the outside of the tire. The liner prevents the tire from leaking internal pressure air. However, during vulcanization molding, if the inner surface of the green tire is partly strongly pressed by the depressions or projections on the outer surface of the bladder, the inner liner at that portion becomes thin, and in severe cases, the carcass cord. There is a concern that internal air may leak due to exposed parts.

However, according to the present invention, the green tire is uniformly pressed on the entire surface without being strongly pressed even in the above-mentioned depressions and projections, so that the inner pressure liner is not thinned and the inner pressure air is not compressed. No more worrying about leaks. Here, the depressions and protrusions on the outer surface of the bladder corresponding to the protrusions and depressions on the inner surface of the mold are formed by changing the thickness of the bladder regardless of the expansion rate of the bladder.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view in the mold width direction showing a state in which a green tire 1 is filled in a bladder 3 with a pressurized fluid in a mold 2 according to the method of the present invention and a bladder to be used for vulcanization. This is an example of the case where the bladder 3 is provided with one protrusion and one depression. Since the tire to be vulcanized and molded has a structure which is substantially symmetrical with respect to the equatorial plane S, only a half of the structure is shown here for simplification.

The green tire 1 has a side wall portion 6 and a tread portion thereof which are formed by a carcass 5 formed of a cord ply of a toroidal radial arrangement straddling a pair of bead portions 4 spaced apart from each other in the direction of the rotation axis thereof. The carcass 5 has a skeleton structure that reinforces the cord 7, and at least one layer of the cord ply has the bead 4
It has a turn-up structure wound around the bead core 8 from the inside of the tire to the outside. In the green tire 1 of this example, the carcass 5 is formed by one cord ply, but the number of plies can be plural layers depending on the tire specifications. Further, in the tread portion 7 forming the tire tread surface, a belt 9 composed of a plurality of (two in FIG. 1) cord arrangement layers is arranged on the outer peripheral side of the crown portion of the carcass 5.

On the other hand, the mold 2 is formed in the circumferential direction of the mold 2 on the inner surface portion corresponding to the required position between the vicinity of the shoulder portion 10 and the vicinity of the bead portion 4 of the tire obtained by vulcanization molding. It has a projection 11 that extends continuously and projects to the inside of the mold 2 (toward the equatorial plane S). The protrusion 11 has an arc portion 11a whose center of curvature is located outside the inner surface of the mold 2 in the widthwise cross section of the mold 2.
And the center of curvature is located inside and outside of the arc portion 11a in the radial direction of the mold, the center of curvature is placed inside the inner surface of the mold 2, and the contour shape is formed by the other two arc portions 11b that are smoothly continuous to the arc portion 11a. Identified, mold 2
Has a convex shape toward the inside.

Further, the mold 2 is provided on the inner surface portion of the tire obtained by vulcanization molding, which corresponds to another required position between the vicinity of the shoulder portion 10 and the vicinity of the bead portion 4. The mold 2 is provided with a recessed portion 12 which extends continuously in the circumferential direction and in which the inner surface of the mold 2 is recessed. The recess 12 is adjacent to an arc portion 12a having a center of curvature inside the inner surface of the mold 2 in the cross section in the width direction of the mold 2 and to the inside and outside of the arc portion 12a in the mold radial direction, and the inner surface of the mold 2. The other two arcuate portions 12 that have a center of curvature on the outer side and smoothly continue to the arcuate portion 12a
The contour shape is specified by b, and a concave shape is formed toward the outside of the mold 2.

On the other hand, the bladder 3 is according to the invention of claim 2, and the outer surface of the bladder 3 is provided with a recess 13 having a shape similar to that of the protrusion 11 at a portion corresponding to the protrusion 11. A protrusion 14 having a shape similar to that of the depression 12 is formed in a portion corresponding to the depression 12. The thickness of the bladder 3 in the area where the protrusion 14 is formed is thicker than other areas, and the thickness of the bladder 3 in the area where the recess 13 is formed is thinner than other areas. Has become. The inner surface of the bladder 3 has no unevenness corresponding to the protrusion 14 or the recess 13.

In order to vulcanize and mold the green tire 1 with the mold 2 and the bladder 3, the green tire 1 is placed in the mold 2 having the protrusion 11 and the recess 12 on the inner surface and the mold is closed. The bladder 3 arranged in the green tire 1 is filled with a pressurized fluid, and the green tire 1 is heated while being pressed against the inner surface of the mold 2. As a result, a radial tire is obtained in which the carcass portions of the green tire 1 corresponding to the protrusions 11 and the depressions 12 deviate inward and outward of the natural equilibrium shape shown by the dotted lines, respectively. Reference numeral 14 is a protrusion provided on the inner surface of the mold for forming a groove on the tire tread surface to be vulcanized and molded. Further, the dotted line portion in the figure shows the outer contour shape of the tire and the carcass line when vulcanization molding is performed using a known mold, and means a natural equilibrium shape.

[Embodiment] The embodiment has been described above with reference to FIG. When the tire vulcanized and molded in this manner is filled with the internal pressure air, the carcass portion that is displaced inward and outward of the tire is swelled to the outside of the tire with the bulging movement to the outside of the tire. Since the tension load on the carcass part of the carcass part changes, the rigidity of each carcass part, and by extension,
The rigidity of the belt end portion and the sidewall portion of the tire can be changed according to the purpose, and therefore, the tire steering stability, vibration riding comfort, rolling resistance, etc. can be changed without changing the known tire constituent members. It is possible to extremely effectively improve various exercise performances. The protrusion 11 or the recess 12 formed on the inner surface of the mold 2 or the protrusion 11 and the recess 12 are formed on the shoulder portion 1 of the tire.
It can also be located above zero.

[Comparative Example] The following is a description with reference to FIG. Except for the bladder 15, it is the same as the embodiment. Therefore, only different parts will be described. The bladder 15 has been used conventionally, and the outer surface thereof is not provided with a recess or a projection corresponding to the projection 11 or the recess 12 provided on the inner surface of the mold 2. The bladder 15 is filled with a pressurized fluid, and the green tire 1 is heated while being pressed against the inner surface of the mold 2 for vulcanization molding. Then, the rubber portion of the green tire 1 is softened by being heated and the fluidity is increased, so that the rubber also flows into the recessed portion 12 formed on the inner surface of the mold 2 and the side wall portion 6 of the green tire 1 is also rubbed. The outer contour shape of is shifted inward and outward from the natural equilibrium shape indicated by the dotted line, and it seems that there is no problem.

However, from Table 1 comparing the wall thicknesses of the tire sidewalls after vulcanization molding corresponding to the protrusions 11 or the depressions 12 provided on the inner surface of the mold 2 obtained in Comparative Example and Example. As is apparent, the wall thickness of the tire sidewall after vulcanization molding corresponding to the depression 12 is 2.9 mm in the example and 4.5 mm in the comparative example with respect to the target value of 2.5 mm. This means that the pressing force by the outer surface of the conventional bladder 15 is insufficient at the portion corresponding to the recessed portion 12, and the carcass 5 is hardly displaced outward. Further, the wall thickness of the tire sidewall after vulcanization molding corresponding to the protrusion 11 is a target value of 2.
Compared to 0 mm, the thickness of the comparative example is 0.5 mm, which is very thin, but that of the embodiment is 2.3 mm, which is close to the target value. As described above, according to the conventional bladder 15, it is shown that the carcass 5 is hardly deviated inward or outward from the natural equilibrium shape. As described above, if the carcass 5 does not deviate, the rigidity of the carcass portion as described above cannot be largely changed, and consequently various exercise performances of the tire cannot be improved.

[0020]

[Table 1]

[0021]

As is apparent from the above description, according to the method and the bladder of the present invention, a tire in which the carcass portion of the tire is complicatedly displaced can be accurately and accurately displaced. Since it can be vulcanized and molded, the rigidity of the required portion of the tire carcass can be partially changed according to the purpose, and the running performance of the tire during running can be greatly improved.

[Brief description of drawings]

FIG. 1 is a state in which vulcanization molding is performed by the method of the present invention,
It is a partial sectional view showing a bladder according to the present invention.

FIG. 2 is a partial cross-sectional view showing a state in which vulcanization molding is performed by a conventional method and a conventional bladder.

[Explanation of symbols]

1: Green tire 2: Mold 3: Bladder 4: Bead part 5: Carcass 6: Side wall part 7: Tread part 8: Bead core 9: Belt 10: Shoulder part 11: Protrusion part 11a, 11b: Arc part 12: Recessed part 12a, 12b: Arc part 13: Dimple part 14: Projection part 15: Bladder

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display area B29L 30:00

Claims (2)

[Claims] 1. A side end portion of at least one cord ply of a carcass consisting of cord plies having a toroidal radial arrangement straddling a pair of bead portions, and a plurality of plural cord plies are wound around the bead core from inside to outside of the tire. On the inner surface of the green tire formed by arranging the belt formed of the cord arrangement layer on the outer peripheral side of the crown portion of the carcass,
When manufacturing a pneumatic radial tire by vulcanizing and molding a green tire with the bladder inscribed, the mold inner surface corresponding to the required position between the shoulder part and the bead part of the manufactured tire Part of the arc, which has a center of curvature outside the inner surface of the mold, and each arc part that is adjacent to the inside and the outside of the arc in the mold radial direction and has a center of curvature inside the inner surface of the mold and that smoothly continues to the arc. And at least one projecting portion that extends inward in the mold and extends continuously in the mold circumferential direction, and that separates between the vicinity of the shoulder portion and the vicinity of the bead portion of the manufactured tire. On the inner surface of the mold that corresponds to the required position, an arc part with the center of curvature inside the inner surface of the mold, and inside and outside of the arc part in the radial direction of the mold. Adjacent to the inner surface of the mold, the center of curvature is placed, and the inner surface of the mold is dented by being divided by the respective arc portions that are smoothly continuous to the arc portion, and at least one dent portion that continuously extends in the mold circumferential direction is provided. On the other hand, on the outer surface of the bladder corresponding to the projection and the depression provided on the inner surface of the mold, the projection and the depression are provided in the bladder in the mold. Inner contact with the inner surface of the green tire filled with internal pressure, by vulcanizing the green tire while maintaining the natural equilibrium shape on the inner surface of the bladder, the carcass part from the natural equilibrium shape by the protrusions and depressions of the tire A method for manufacturing a pneumatic radial tire, which comprises displacing both inward and outward. 2. An arc portion having a center of curvature outside the inner surface of the mold and a mold of the arc portion in the mold inner surface portion corresponding to a required position between the shoulder portion and the bead portion of a tire to be manufactured. At least one of which is adjacent to the inner and outer sides in the radial direction and is centered on the inner side of the inner surface of the mold and which is defined by the respective arc portions that are smoothly continuous to the arc portion and protrudes inward of the mold, and extends continuously in the mold circumferential direction. A circular arc with a center of curvature inside the mold inner surface corresponding to another required position between the vicinity of the shoulder portion and the vicinity of the bead portion of the manufactured tire. And a circular arc portion that is adjacent to the inside and outside of the circular arc portion in the mold radial direction and has a center of curvature outside the inner surface of the mold and that smoothly continues to the circular arc portion. A bladder used for vulcanization molding of a tire together with a mold in which the inner surface of the mold is dented to form a dent, and at least one dent portion that continuously extends in the mold circumferential direction is provided, and the protrusion of the mold inner surface is provided. A bladder formed by changing the thickness of the bladder on the outer surface of the bladder corresponding to the recess and the recess, the recess and the protrusion having a shape substantially similar to the projection and the recess.