JP2003039570A - Pneumatic tire and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce molding failure. SOLUTION: The method for manufacturing a pneumatic tire having a bead apex rubber 9 extending from a bead core 5 to the outside of a radial direction in its bead 4 is disclosed. This manufacturing method includes a process for molding a tire green cover RT using an unvulcanized bead apex rubber 9R having a non-smooth uneven region 12 provided to the inner surface 9i or outer surface 9o thereof in a tire axis direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire manufacturing method and a pneumatic tire capable of reducing defective molding.

[0002]

2. Description of the Related Art Pneumatic tires have a carcass ply in which a carcass cord is covered with unvulcanized topping rubber, a tread rubber formed from unvulcanized rubber, sidewall rubber, bead apex rubber, etc. It is manufactured by molding a toroidal tire raw cover and vulcanizing it with a mold.

[0003]

Since each of the above-mentioned members is covered with rubber or the surface thereof is covered with a topping rubber or the like, the bonding surface has adhesiveness. Therefore, when these members are bonded together, air is easily trapped between the members, and once the air is trapped, it is difficult to discharge the air. Particularly, in the bonding surface of the sidewall rubber and the bead apex rubber, etc., since both of them have a smooth bonding surface, air is easily trapped. The air trapped in the bonding surface of each member is liable to cause a molding defect such as a so-called defect in which the outer surface is distorted or a bear in which the outer surface is dented.

The present invention has been devised in view of the above problems, and uses a non-vulcanized bead apex rubber provided with a non-smooth uneven surface on an inner surface or an outer surface in the tire axial direction. Air that can reduce molding defects by reducing the adhesiveness of this bead apex rubber to make it difficult to trap air during lamination and to disperse the trapped air, etc. It is intended to provide a method for manufacturing a filled tire.

In the invention according to claim 6, the bead apex rubber is manufactured by the above-mentioned method, for example, and the bead apex rubber has a non-smooth uneven region on the inner or outer surface in the tire axial direction to reduce molding defects. The purpose of the present invention is to provide a possible pneumatic tire.

[0006]

According to a first aspect of the present invention, there is provided a pneumatic tire manufacturing method for manufacturing a pneumatic tire having a bead apex rubber extending from a bead core to a tire radial outside in a bead portion. The method is characterized by including a step of molding a raw tire cover using an unvulcanized bead apex rubber in which a non-smooth uneven region is provided on an inner surface or an outer surface in the tire axial direction.

The invention according to claim 2 is the method for manufacturing a pneumatic tire according to claim 1, wherein the concave-convex region is formed by separating a plurality of concave grooves.

According to a third aspect of the invention, the concave groove is
The method for producing a pneumatic tire according to claim 2, wherein the method extends in the tire radial direction.

According to a fourth aspect of the invention, the concave groove is
The pneumatic tire manufacturing method according to claim 2, wherein the pneumatic tire is inclined with respect to the tire radial direction.

According to a fifth aspect of the invention, the groove is
The depth is 0.5-1.5 mm and the pitch is 1.5-
It is 5.0 mm, It is a manufacturing method of the pneumatic tire in any one of Claims 2 thru | or 4 characterized by the above-mentioned.

According to the invention of claim 6, in the bead portion,
A pneumatic tire having a bead apex rubber extending from a bead core to a tire radial direction outer side, wherein the bead apex rubber is a pneumatic tire characterized by having a non-smooth uneven region on an inner surface or an outer surface in a tire axial direction. is there.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 illustrates a pneumatic tire 1 manufactured by the manufacturing method of the present invention. In the figure, a pneumatic tire 1 has a toroidal carcass 6 extending from a tread portion 2 to a bead core 5 of a bead portion 4 through a sidewall portion 3, and a carcass 6 disposed outside the carcass 6 in the tire radial direction and inside the tread portion 2. This example illustrates a radial tire for a passenger vehicle, which has a belt layer 7 made of steel cord.

The carcass 6 has at least one carcass ply 6A having a radial structure in which carcass cords are arranged at an angle of, for example, 90 ° with respect to the tire equator C, and in this example, one carcass ply 6A.
It consists of The carcass ply 6A is formed by thinly covering the surface of the aligned body of the carcass cord with topping rubber. As the carcass cord, for example, an organic fiber cord, in this example, a polyester cord is adopted, but the carcass cord is not limited to this.

The carcass ply 6A includes a main body portion 6a extending from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4 and an inner side in the tire axial direction around the bead core 5 extending from the main body portion 6a. And a folded-back portion 6b that is folded back from the outside. A bead apex rubber 9 is provided between the main body portion 6a and the folded-back portion 6b so as to extend outward from the bead core 5 in the tire radial direction. Further, the folded portion 6b of the present embodiment has a low turn-up structure in which the height h1 of the outer end 6be of the bead apex rubber 9 from the bead base line BL is smaller than the height h2 of the outer end 9e of the bead apex rubber 9 ( Specifically, it has a 1-0 low turn-up structure).

In the sidewall portion 3, a sidewall rubber 10 is provided outside the carcass 6 in the tire axial direction.
However, the tread rubber 11 is arranged on the outer side in the tire radial direction of the tread portion 2. Sidewall rubber 1
The carcass ply 6A has a low turn-up structure, so that the carcass ply 6A has a rubber-bonded portion j1 directly bonded to the bead apex rubber 9 in a region radially outside the outer end 6be of the folded-back portion 6b.

FIG. 2 schematically shows the bead portion 4 of the tire raw cover before vulcanization of such a pneumatic tire 1.
As is clear from FIG. 2, the pneumatic tire 1 of the present embodiment is a tire tire using unvulcanized bead apex rubber 9R in which an uneven surface area 12 is provided on the inner surface 9i or the outer surface 9o in the tire axial direction. It is manufactured including a step of molding the cover.

The raw tire cover RT is molded by a conventional method, for example, using a molding drum. For example, FIG.
As shown in (C), an inner liner (not shown), a carcass ply 6A, a bead core 5, and a bead apex rubber 9R are arranged on a cylindrical molding drum 20 to wind up both ends of the carcass ply 6A (Fig. (A)). ). Then, the side wall rubber 10 is arranged (FIG. 2B), and the side wall rubber 10 is shaped into a toroidal shape and integrated with the belt layer 7 and the tread rubber 11. Further, the concave-convex area 12 of the present embodiment is, for example, as shown in FIG.
The unvulcanized bead apex rubber 9R is formed on the outer surface 9o with a plurality of recessed grooves 13 extending in the tire radial direction.

5 (A) and 5 (B) schematically show the bead portion. As shown in FIG. 5 (A), in the pneumatic tire 1 having a low turn-up structure, the rubber-bonded portion j1 in which the sidewall rubber 10 and the bead apex rubber 9R, which are both formed only of rubber and have high adhesiveness, are directly bonded to each other. Have. The rubber-bonded portion j1 has a high degree of adhesion at the time of bonding when the raw tire cover is molded, and air traps easily occur. On the other hand, like the present embodiment, the outer surface 9 of the unvulcanized bead apex rubber 9R is
By forming the concavo-convex region 12 in o, the degree of adhesion at the rubber-bonded portion j1 can be appropriately reduced and the trapping of air can be suppressed.

That is, unvulcanized bead apex rubber 9
Since the concave-convex region 12 is formed on the outer surface 9o of the R, the initial surface area at the time of bonding, which is in contact with the mating side at the initial stage of bonding, is reduced by the concave groove 13. Therefore, the apparent adhesion of the outer surface 9o of the bead apex rubber 9R can be reduced. As a result, the degree of adhesion at the rubber-bonded portion j1 can be appropriately reduced, and a large number of minute gaps through which air can come and go can be formed in the bonding surface. Then, during the shaping process or the vulcanization process, the air can be smoothly moved and dispersed in the concavo-convex region 12 of the bead apex rubber 9R, so that it is possible to prevent the formation of a concentrated lump of air in one place. This can reduce molding defects such as defects and bares during the tire vulcanization process. Further, since the concave-convex region 12 is formed by arranging a large number of concave grooves 13 separately, it is possible to smoothly move air in and out of the groove and efficiently disperse the air.

As described above, the present invention can be particularly preferably applied to the production of a pneumatic tire having a rotary up structure having a rubber-bonded portion ji. On the other hand, as shown in FIG. 5B, the outer end 6be of the folded-back portion 6b of the carcass ply 6A.
However, in the case of a pneumatic tire having a high turn-up structure located higher than the outer end 9e of the bead apex rubber 9, the inner surface 9i and the outer surface 9o of the bead apex rubber 9R are
And the carcass ply 6A are directly attached to each other-
A rubber-bonded portion j2 is formed. The unvulcanized carcass ply 6A has a slightly wavy surface as compared with the sidewall rubber 10. Therefore, the adhesion degree of the ply-rubber bonded portion j2 can be lower than that of the rubber bonded portion ji.

However, by providing the concave-convex regions 12 on the outer surfaces 9i, 9o of the bead apex rubber 9R, it is possible to reliably prevent the occurrence of air pockets even in such a ply-rubber bonded portion j2 and reduce molding defects. To help. In recent years, in a pneumatic tire having a high turn-up structure, an insulation rubber sheet (not shown) having a small thickness may be interposed between the carcass ply 6A and the bead apex rubber 9R. In this case, since the rubber affixed portion ji is formed on the bead apex rubber 9R even with the high turn-up structure, it is possible to effectively prevent defective molding by applying the present invention. That is, the method for producing a pneumatic tire of the present invention is not limited to the pneumatic tire having a rot up structure.

Incidentally, it is possible to reduce the tackiness of the bead apex rubber 9R itself by improving the rubber composition. However, such a method is not preferable because the tackiness of the material is severely affected by changes in climate, temperature during storage, variations in formulation, and the like, which makes management difficult and results in poor productivity.

As shown in FIGS. 2 and 3 (A), the groove 13 is formed as a groove extending in the tire radial direction in this embodiment. Such a groove 13 can function as if it were a vent line, for example. That is, the uneven region 12 of the rubber-bonded portion j1
In, it is possible to allow air to move in and out in the radial direction of the tire. It should be noted that the portion where the carcass ply 6A and the sidewall rubber 10 are bonded together can allow the air to move by utilizing the original unevenness of the carcass ply 6A. Particularly in the vicinity of the bead core, since there are many steps and air easily collects, the air in such a portion is moved to the outside in the radial direction of the tire by utilizing the concave groove 13 of the concave-convex region 12, dispersed, and discharged.
Molding defects can be reduced more reliably.

The depth and pitch of the grooves 13 are not particularly limited, but preferably, as shown in FIG. 4 which is a cross section taken along the line AA of FIG. 5 to 1.5
mm, and the spacing pitch P is preferably 1.5 to 5.0 mm. When the groove depth is less than 0.5 mm, the adhesive force is less likely to decrease in the bonding surface, and the unevenness is easily crushed by the deformation in the bonding surface, and there is a minute gap that allows air to move. Tends to be less. On the contrary, if the groove depth of the concave groove 13 exceeds 1.5 mm, it is not preferable because more air tends to be held during the bonding.

Similarly, when the spacing pitch P of the concave grooves 3 is less than 1.5 mm, the adhesiveness of the concave and convex regions 12 is excessively reduced, or the bead apex rubber 9R is curled during storage. When the raw tire cover is molded, the workability is poor, and when it exceeds 5.0 mm, the effect of air migration and dispersion tends to be relatively reduced. Particularly preferably, the spacing pitch P of the recessed grooves 3 is 1.5 to 4.0 mm, and more preferably 1.5 to 3.0 mm. The spacing pitch P of the grooves 13 is measured as the distance between the center lines of the groove width.

The groove sectional shape of the concave groove 13 is shown in FIG.
In addition to the triangular shapes shown in (A) and (D), various shapes such as the rectangular shape shown in FIG. 2B, the circular arc shape shown in FIG. 7C, and the composite shape in which the circular arc shown in FIG. Can be adopted. Further, the groove width of the concave groove 13 is not particularly limited, but preferably, the preferable range of the groove depth d can be similarly applied.

The uneven area 12 has a groove 13 extending in the tire radial direction as shown in FIG. 3 (A), and the tire radius as shown in FIGS. 3 (B) and 3 (C). It is also possible to dispose the concave grooves 13 inclined with respect to the direction, or to provide the concave grooves 13 intersecting in a lattice pattern as shown in FIG. Further, in this example, the concave groove 13 extends linearly, but it goes without saying that the groove 13 may be formed in various shapes such as a curved line, a zigzag pattern, and a wavy pattern. Also in this example,
Although the concavo-convex region 12 is formed on substantially the entire outer surface 9o of the bead apex rubber 9R, it may be provided only on a part of the inner surface 9i or the outer surface 9o.

The unvulcanized bead apex rubber 9R having the uneven areas 12 is extruded using a die plate D composed of an upper die D1 and a lower die D2, as shown in FIG. 6, for example. You can Die plate D
Are formed on the inner surface 9i and the outer surface 9o of the bead apex rubber 9 on the uneven surfaces Ea and Eb.
An opening E having an opening E is formed, and a bead apex rubber 9R as shown in FIG. 3B can be molded by extruding a rubber material extruded from the extruder through the opening E.

Further, as shown in FIG. 7, a bead apex rubber 9R which is separately extruded is passed between the rollers of a stamper comprising a pair of rollers R1 and R2 on the surface of which gear-shaped uneven portions Ec and Ed are formed. By doing so, the bead apex rubber 9R as shown in FIGS. 3A, 3C, and 3D can be molded. Note that these methods are merely examples, and it goes without saying that the bead apex rubber 9R having the concavo-convex regions 12 can be molded by various methods.

Further, the uneven region 12 is not limited to the concave groove 13 as long as it makes the surface of the inner surface 9i or the outer surface 9o of the bead apex rubber 9R non-smooth.
For example, it may be formed by sparsely forming dot-shaped small recesses (not shown). In this case, the preferable value of the depth of the small recesses may be the same as that of the recesses 13.

The pneumatic tire 1 manufactured in this manner has the inside of the concave groove 13 in the concave-convex region of the bead apex 9R during vulcanization, as shown in the enlarged YY section of FIG. Although the rubber of the other member enters into and is integrated with the rubber, the uneven region 12 formed on the outer surface 9o of the bead apex rubber 9 in the tire axial direction may remain even after the molding, but in general, as shown in FIG. Due to the above process, most of them tend to be flattened while allowing air to escape.

[0032]

Example: Tire size is 175 / 70R13 (1-0
A pneumatic tire having a low turn-up structure was manufactured according to the present invention (Example), and moldability and defective rate were investigated. Further, in order to compare the performance, a tire was manufactured by using a bead apex rubber having the same size and not having a concavo-convex region (conventional example), and similarly, the moldability and the defective rate were investigated.

The specifications of the concave and convex regions of each bead apex rubber are as shown in Table 1. Regarding "moldability", the deformation state of the bead apex rubber in the stock was visually examined. As for the "defective rate", 500 tires were manufactured for each, and the defective rate in which molding defects such as defects and bares occurred were examined, and displayed as an index with the defective rate of the conventional example being 100. The smaller the value, the smaller the defective rate and the better. The test results are shown in Table 1.

[0034]

[Table 1]

As a result of the test, it can be confirmed that the example has less molding defects than the conventional example. Even when the bead apex rubber is provided with an uneven area,
There was a bead apex rubber that was slightly deformed,
No major problems occurred during manufacturing.

[0036]

As described above, according to the first aspect of the present invention, the tire raw cover is molded by using the unvulcanized bead apex rubber provided with the uneven surface on the inner or outer surface in the tire axial direction. Including steps. Since the adhesiveness of the concave and convex regions of the bead apex rubber is reduced, it is possible to suppress the entrapment of air during the bonding with other members.
Therefore, molding defects are reduced. In addition, even when air is trapped, it is possible to move air in and out of the concavo-convex area, and it is possible to move, disperse, and discharge air in the bonding surface, and in particular to prevent the occurrence of local air traps and to prevent defects, etc. Molding defects can be effectively prevented.

When the concavo-convex region is formed by separating a plurality of recessed grooves, the recessed grooves function as if they were bent lines, which is more effective. It is possible to disperse air within the bonding surface of the bead apex rubber.

When the groove is extended in the tire radial direction, the air on the bead core side where air is particularly likely to accumulate is utilized outside in the tire radial direction by utilizing the groove in the uneven region. It is possible to efficiently shift to, disperse, and discharge, and molding defects can be reduced more reliably.

[0039] Further, as in the invention according to claim 4, when the groove extends obliquely with respect to the tire radial direction,
In particular, air on the bead core side where air tends to accumulate can be transferred to the outside in the radial direction of the tire by utilizing the concave grooves of the concave-convex region and dispersed, and molding defects can be more reliably reduced.

When the depth of the concave groove and the spacing pitch are limited as in the fifth aspect of the present invention, defective molding can be more reliably reduced.

Further, in the pneumatic tire having the bead apex rubber extending from the bead core to the outer side in the tire radial direction in the bead portion,
When the bead apex rubber has a non-smooth uneven area on the inner or outer surface in the tire axial direction, the uneven area is used during molding of the tire raw cover to suppress air entrapment during bonding with other members. it can.
Therefore, molding defects are reduced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a pneumatic tire manufactured by a manufacturing method of the present invention.

FIG. 2 is a partial perspective view showing a bead portion of a tire raw cover.

FIG. 3A to FIG. 3D are partial perspective views illustrating an unvulcanized bead apex rubber.

4 (A) to (D) are cross-sectional views showing an example of unvulcanized bead apex rubber.

FIG. 5A is a schematic diagram of rotation up, and FIG. 5B is a schematic diagram of high turnup.

FIG. 6 is a cross-sectional view of a die plate for molding bead apex rubber.

FIG. 7 is a perspective view of a stamper for molding bead apex rubber.

8 is a cross-sectional view taken along line YY of FIG.

9A to 9C are schematic cross-sectional views showing an example of a molding process of a tire raw cover.

[Explanation of symbols]

2 tread section 3 Side wall part 4 bead section 5 bead core 6 carcass 6A carcass ply 7 Belt layer 9,9R Bead apex rubber 10 Sidewall rubber 12 uneven area 13 groove

Claims (6)

[Claims] 1. A pneumatic tire manufacturing method for manufacturing a pneumatic tire having a bead apex rubber extending from a bead core to a tire radial outer side in a bead portion, wherein the inner surface or the outer surface in the tire axial direction has unevenness. A method for manufacturing a pneumatic tire, comprising a step of molding a raw tire cover using an unvulcanized bead apex rubber provided with a region. 2. The method of manufacturing a pneumatic tire according to claim 1, wherein the uneven region is formed by arranging a plurality of concave grooves. 3. The method of manufacturing a pneumatic tire according to claim 2, wherein the groove extends in the tire radial direction. 4. The method for manufacturing a pneumatic tire according to claim 2, wherein the groove extends obliquely with respect to the tire radial direction. 5. The groove has a depth of 0.5 to 1.5 mm.
The method for producing a pneumatic tire according to any one of claims 2 to 4, wherein the pitch is 1.5 to 5.0 mm. 6. A pneumatic tire having a bead apex rubber extending from a bead core to a tire radial outside in a bead portion, wherein the bead apex rubber has a non-smooth uneven region on an inner surface or an outer surface in a tire axial direction. A pneumatic tire characterized by the following.