JPH11320705A - Production of pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the bare generation rate of a bead part. SOLUTION: The raw cover of a tire has a carcass 9 which starts from a tread part, passes through a side wall part, and fitted to the bead core 7 of a bead part 6 and side wall rubber 12 which is arranged on the carcass outer surface of the side wall part 5 and the radius direction inner end of which is connected to a bead chafer which reinforces a bead sheet surface. The raw cover, inserted into a mold, is vulcanized by a process in which a boundary part S between the side wall rubber 12 and the bead chafer 13 positions a side wall rubber edge E appearing on a raw cover outer surface 2a to the radius direction outside from the core outward point P1 of the raw cover outer surface or the radius direction inside from the core inward point 6 P2.

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 tire capable of suitably preventing the occurrence of a bear near a sidewall rubber edge.

[0002]

2. Description of the Related Art In recent years,
Tires for passenger cars, mainly sedans, are strongly required to have improved quietness (noise performance) and riding comfort when running. In recent years, in order to improve noise performance and ride comfort, in radial tires for passenger cars, a mono-ply construction in which the carcass is composed of a single carcass ply, and a cord reinforcement that is separately arranged in the bead portion from the carcass are provided. Fillerless technology has been used to reduce the number of layers and the like to reduce bead rigidity.

However, it has been found that when such tires are produced, the rate of occurrence of bears at the bead portion becomes higher than that of conventional tires. Note that the bare refers to a problem that when a green cover of a tire is vulcanized with a mold, air between the green cover and the mold remains and a dent or the like occurs on the surface of the vulcanized tire.

The present inventors have conducted intensive studies to reduce the occurrence of such a bear. As shown in FIG. 7, most of the bears c at the bead portion b are formed of tires made of sidewall rubber a. The edges e of the sidewall rubber a are both generated in a concentrated manner near the radially inner edge e, and in the raw cover t of the tire inserted into the mold m as shown in FIG. Since the axial line passing through the inner end and the outer end of the very hard bead core f substantially made of a non-extensible material is located between the positions fd and fu which intersect the outer surface of the raw cover, the bead core f and the mold m , It was found that it was firmly sandwiched from both sides in the axial direction.

[0005] Predetermined markings and the like are applied to the outer surface of the bead portion of the raw cover t of the tire before vulcanization, and the deformation behavior of the marking is measured after vulcanization to quantify the complicated behavior of the rubber during vulcanization. We tried an experiment to grasp it. From the result shown in FIG. 9, a very large compressive force is acting on the region (between fu and fd) sandwiched between the bead core f and the mold m. It was possible to find out that abnormal deformation of the rubber edge e was the cause of bear generation.

[0006] In addition, as described above, due to the use of a mono-ply or filler-less material, the thickness of the rubber D between the raw cover outer surface g and the bead core f of the raw cover t is reduced, and vulcanization of this portion is performed. It was also found that the lower cushion function in the interior further promoted the occurrence of bears.

In the present invention, in a state where the raw cover is inserted into the mold, the side wall rubber edge is displaced inward or outward in the tire radial direction from between the bead core and the mold to vulcanize the raw cover. On the basis of this, it is an object of the present invention to provide a method for manufacturing a pneumatic tire that can suitably prevent the occurrence of the above-described bear.

According to the third aspect of the present invention, the minimum thickness D of the core transverse rubber between the outer surface of the raw cover and the bead core is provided.
It is an object of the present invention to provide a method of manufacturing a pneumatic tire that can effectively prevent the occurrence of the bear by limiting the diameter of the tire to a predetermined size or more.

According to the present invention, there is provided a method for manufacturing a pneumatic tire which does not impair productivity by preventing an increase in the number of parts when increasing the thickness D of the core transverse rubber. The purpose is.

[0010] According to the fifth aspect of the present invention, a method of manufacturing a pneumatic tire capable of suitably preventing the occurrence of bears in a pneumatic tire capable of improving noise performance and ride comfort by adopting a mono-ply and a filler-less method. It is intended to provide.

[0011]

According to the first aspect of the present invention, there is provided a method of manufacturing a pneumatic tire by manufacturing a pneumatic tire by inserting a green cover of the tire into a mold and vulcanizing and molding. The raw cover is provided on a carcass locked from the tread portion through the sidewall portion to the bead core of the bead portion, and the carcass is disposed on the outer surface of the carcass of the sidewall portion and the radial inner end reinforces the bead seat surface. Sidewall rubber connected to a bead chafer, and a boundary portion between the sidewall rubber and the bead chafer appears on an outer surface of the raw cover when the raw cover is inserted into a mold. Is radially outward from a core outer point P1 where an axial line L1 passing through the tire radial outer end of the bead core and the raw cover outer surface intersect. Alternatively, the raw cover is vulcanized by being positioned radially inward of a core inner point P2 where an axial line L2 passing through the tire radial inner end of the bead core and the raw cover outer surface intersect. It is a manufacturing method of a tire.

According to a second aspect of the present invention, the sidewall rubber is composed of a side base rubber and a clinch rubber harder than the side base rubber connected to a radial inner end of the side base rubber. A method for manufacturing a pneumatic tire according to claim 1, wherein:

According to a third aspect of the present invention, in the green cover, the minimum thickness D of the core transverse rubber between the outer surface of the green cover and the bead core is 2.5 mm or more. Or a method for manufacturing a pneumatic tire according to item 2.

According to a fourth aspect of the present invention, the raw cover includes a main body extending from a tread portion on the inner surface of the tire through a sidewall portion to a bead portion, and a surrounding portion of the bead core connected to the main body portion. The pneumatic tire manufacturing method according to any one of claims 1 to 3, further comprising an inner liner rubber having a folded portion that is folded from inside to outside in the tire axial direction.

According to a fifth aspect of the present invention, in the raw cover, the carcass is made of one carcass ply, and the cord reinforcement of the bead portion is made of only the carcass cord of the carcass ply. 5. A method for manufacturing a pneumatic tire according to any one of 1 to 4.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. The present invention is a method for manufacturing a tire in which a raw cover 2 of a pneumatic tire is inserted into a mold 3 and vulcanized and molded. In the present embodiment, as shown in FIG. 1, the raw cover 2 has a carcass 9 that is locked from a tread portion 4 via a sidewall portion 5 with a bead core 7 of a bead portion 6, and a radius of the carcass 9 inside the tread portion. And a belt layer 10 arranged on the outside in the direction.

In the present embodiment, the carcass 9 is formed of a single carcass ply 9A that is folded back from the inside to the outside in the axial direction so as to enclose the bead apex rubber 8 around the bead core 7, and is locked. The carcass ply 9A is formed by arranging carcass cords made of organic fiber cords such as polyester, nylon or rayon in parallel, and forming an angle of 75 ° to 90 ° with respect to the tire equator C.

In the belt layer 10, in this embodiment, the belt cords are arranged at a small angle of 10 to 40 ° with respect to the tire equator, and the cords intersect two outer belt plies 10A and 10B with each other. It is configured to overlap in the direction. In this embodiment, a steel cord is used as the belt cord, but a high elastic organic fiber cord such as aramid or rayon may be used as necessary.

The raw cover 2 is made of tread rubber 11.
, Sidewall rubber 12 and bead chain 13
And The tread rubber 11 is provided on the belt layer 1.
0, and a predetermined tread pattern is engraved by the tread mold 3a.

The sidewall rubber 12 is disposed on the outer surface of the carcass 9 of the sidewall portion 5 and has a tire radial outer end connected to the tread rubber 11 and a radial inner end connected to the bead chafer 13. Connected to. The side wall rubber 12 has a side base rubber 12a occupying most of the side wall portion 5 and a side base rubber 12a which is harder and smaller in length than the side base rubber connected to the radial inner end of the side base rubber 12a. An example of two types of rubber, the clinch rubber 12b, is shown.

In this example, the bead chafer 13 includes a base 13a extending on the bead seat surface 14 and an outer end in the tire radial direction from both ends in the axial direction of the base 13a, as shown in FIG. External launcher 13
i and 13o, and a rubber-coated canvas portion 13B wrapping the hard rubber portion 13A from outside. Bead chafer 13
Is provided on the bead portion 6 before the sidewall rubber 12 is attached, and the hard rubber portion 13A
By vulcanization, it becomes harder than the clinch rubber 12b.
The bead chafer 13 protects the bead seat surface 14 after the rim is assembled and secures its rigidity.

Further, the raw cover 2 of the present embodiment shows that the carcass 9 is formed of one carcass ply 9A and the bead portion 6 is reinforced only with the carcass cord of the carcass ply 9A. Therefore, a pneumatic tire that can improve noise performance and ride comfort by vulcanizing the green cover 2 can be obtained.

The mold 3 can be of various types. In the present embodiment, a tread mold 3a capable of forming a tread pattern on the tread rubber 11, and a side wall portion 5 and a bead This shows an upper mold 3b and a lower mold 3c that can form the part 6 and that can freely contact and separate.

In the present invention, when the raw cover 2 is inserted into the mold 3, the boundary S between the sidewall rubber 12 and the bead chafer 13 is formed as shown in FIGS. The sidewall rubber edge E appearing on the outer surface 2a is radially outside the core outer point P1 where the axial line L1 passing through the tire radial outer end of the bead core 7 and the raw cover outer surface 2a intersect, or the tire of the bead core 7 The raw cover 2 is vulcanized by being positioned radially inward of the core inner point P2 where the axial line L2 passing through the radial inner end and the raw cover outer surface 2a intersect.

As a result, in this embodiment, it is possible to prevent a large compressive force from acting on the sidewall rubber edge E during vulcanization and suppress abnormal deformation thereof. Generation of bears near the wall rubber edge E can be effectively suppressed. Here, the state in which the raw cover 2 is inserted into the mold 3 refers to a state in which the molds 3a to 3c of the mold 3 are closed, and this is performed by using a plaster piece having the same molding surface as the mold. It is possible to confirm.

In the present invention, it is important to specify the position of the sidewall rubber edge E in a state where the raw cover 2 is inserted into the mold 3, and where the sidewall rubber edge E is located in the vulcanized finished tire. It does not matter much from the standpoint of bear prevention. Note that the sidewall rubber edge E changes its radial position before and after vulcanization. Therefore, for the finished tire after vulcanization manufactured by the method of the present invention, the sidewall rubber edge E is located between the core outer point P1 and the core inside. It may be located between the direction point P2.

In this embodiment, as shown in FIG. 2, the clinch rubber 12b of the sidewall rubber 12 is formed in a tapered shape whose thickness gradually decreases toward the sidewall rubber edge E, and the canvas portion of the bead chafer 13 is formed. 13
B illustrates an example in which the side wall rubber edge E is connected to the outer surface of B and the sidewall rubber edge E is positioned radially outward from the core outer point P1. The positioning of the side wall rubber edge E is determined by the position where the side wall rubber 12 is attached and the side wall rubber 1 at the time of molding the raw cover.
It can be easily achieved by adjusting the width dimension of 2, for example.

In this embodiment, the position of the sidewall rubber edge E can be variously set according to the type and size of the tire. For example, the height h1 from the axial line L1 passing through the core outer point P1 can be set. However, it is preferably 0.5 mm or more, more preferably 1.0 mm or more, and still more preferably 1.5 mm or more. If the height h1 is too large, the clinch rubber 12b cannot sufficiently contact the rim in the finished tire and the rim may shift, so the upper limit of each of the above values is preferably set to 5.0 mm.

The raw cover 2 has a minimum thickness D (see FIG. 2) of the core lateral rubber 15 between the raw cover outer surface 2a and the bead core 7 while achieving mono-ply and filler-less.
) Of which 2.5 mm or more is secured.

In general, when the raw cover 2 is made of a monoply or filler-less material, the core lateral rubber 15 tends to be thin. For example, in the case of a radial tire for a passenger car, the minimum thickness D of the core lateral rubber 15 is Approximately 1.9-2.0mm
And the cushion effect at this portion tends to decrease. The present inventor has found that as a result of various experiments, when the cushioning effect of the core lateral rubber 15 is reduced, a bear easily occurs.

Therefore, the raw cover outer surface 2a and the bead core 7
By limiting the minimum thickness D of the core horizontal rubber 15 to 2.5 mm or more, the cushion effect of this portion can be maintained during vulcanization, and the effect of suppressing the bear can be further enhanced. . The minimum thickness D is, for example, 2.5 to 3.7 mm, and more preferably 2.5 to 2.9 mm.
It is particularly desirable that

In the present embodiment, in order to increase the minimum thickness D of the core lateral rubber 15, a main body portion 16 a which is arranged on the inner surface of the tire and extends from the tread portion 4 to the bead portion 6 through the sidewall portion 5 is formed. The inner liner rubber 16 having a folded portion 16b which is integrally connected to the main body 16a and which is folded around the bead core 7 from the inside to the outside in the tire axial direction is illustrated. As described above, the folded portion 16b of the inner liner rubber is connected to the core horizontal rubber 1.
5, the thickness D of the core lateral rubber 15
Therefore, the thickness of the core lateral rubber 15 can be increased without increasing the number of parts.

FIG. 3 shows another embodiment of the raw cover 2. In this example, the bead chafer 13 has a base portion 13a extending on the bead seat surface 14, a hard rubber portion 13A including only a rising portion 13i rising from the inside in the axial direction of the base portion 13a to the outside in the tire radial direction, and A rubber-covered canvas portion 13B wrapping the hard rubber portion 13A from the outside.

In this example, the clinch rubber 12b of the sidewall rubber 12 extends to the bead seat surface 14, and the sidewall rubber edge E is located radially inward of the core inner point P2. Is exemplified. In this example, the position of the sidewall rubber edge E is not particularly limited as long as the sidewall rubber 12 can be attached in the raw cover molding step, but is terminated without reaching the inside of the bead core 7 in the tire radial direction. Is good.

FIG. 4 shows another embodiment of the raw cover 2. In this example, the bead chafer 13 is
A base 13a extending on the bead seat surface 14;
A hard rubber portion 13A having outer rising portions 13i, 13o rising from the inner and outer ends in the axial direction of the tire 3a, and a rubber-coated canvas portion 13B wrapping the rubber portion 13A from the outside. It is composed of The clinch rubber 12b of the sidewall rubber 12 is
This example also illustrates the one extending to the bead seat surface 14.

The embodiment of the present invention has been described in detail above. For example, the sidewall rubber 12 is formed by connecting three or more rubbers in the tire radial direction, and the bead chafer 13 is formed only of hard rubber. The body, or even the raw cover, may comprise a plurality of carcass plies or bead reinforcement layers, and the invention may be modified in various ways.

[0037]

EXAMPLES A tire raw cover having a finished size of 175 / 70R13 was prototyped to test the effect of the production method of the present invention. The test was performed by vulcanizing a tire (Comparative Examples 1 and 2) in which the sidewall rubber edge of the raw cover was positioned between the outer point P1 and the inner point P2 of the core in a state of being inserted into the mold. When the raw rubber is inserted into the mold, the side wall rubber edges of the raw cover
2 and vulcanized molded tires (Examples 1 to
Regarding 4), the occurrence rate of bear near the sidewall rubber edge (n = 200) was examined. Table 1 shows the test results.
Shown in

[0038]

[Table 1]

As a result of the test, it was found that the rate of occurrence of the bear was reduced in the example of the present invention as compared with the comparative example, and at the same time, the minimum thickness D of the core transverse rubber was set to 2.5 mm or more. It was also confirmed that the effect was remarkable. 5 and 6 show the results of examining the forces acting on the bead portion during vulcanization for Examples 2 and 4. As is clear from the figure, it can be confirmed that no large compressive force acts on the sidewall rubber edge E.

[0040]

As described above, according to the first aspect of the present invention, when the raw cover is inserted into the mold, the side wall rubber edge is moved radially outward from the core outer point P1 or toward the core inner point. By vulcanizing the raw cover at a position radially inner than P2, it is possible to prevent a large compressive force from acting on the edge of the sidewall rubber during vulcanization, and to suppress abnormal deformation thereof. Because you can
The occurrence of bears near the edge can be effectively suppressed.

According to the third aspect of the present invention, the raw cover has a minimum thickness D of the core transverse rubber between the outer surface of the raw cover and the bead core of 2.5 mm or more. Can exert a cushioning function, and can further enhance the effect of suppressing bears.

According to the present invention, the inner liner rubber disposed on the inner surface of the tire is folded from the inside to the outside in the tire axial direction around the bead core, so that the number of parts is not increased. It can help increase the thickness of the cross rubber.

According to the fifth aspect of the present invention, the raw cover is made of one carcass ply and the cord reinforcement of the bead portion is made of only the carcass ply of the carcass ply, thereby improving the noise performance and the riding comfort. A pneumatic tire can be manufactured while suppressing the bear at the bead portion.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a state where a raw cover is inserted into a mold.

FIG. 2 is an enlarged view of a bead portion of the raw cover of FIG.

FIG. 3 is an enlarged view showing another example of a bead portion of a raw cover.

FIG. 4 is an enlarged view showing another example of the bead portion of the raw cover.

FIG. 5 is a graph showing a force acting on a bead portion (Example 2) during vulcanization.

FIG. 6 is a graph showing a force acting on a bead portion (Example 4) during vulcanization.

FIG. 7 is a perspective view illustrating a bear at a bead portion of a tire.

FIG. 8 is an enlarged view of a bead portion of a conventional raw cover.

FIG. 9 is a graph showing a force acting on a bead portion during vulcanization by a conventional method.

[Explanation of symbols]

 Reference Signs List 2 raw cover 2a raw cover outer surface 3 mold 4 tread part 5 sidewall part 6 bead part 7 bead core 9 carcass 9A carcass ply 13 bead chafer 14 bead seat surface 15 core horizontal rubber 16 inner liner rubber 16a main body of inner liner rubber 16b Folded portion of inner liner rubber E Sidewall rubber edge P1 Outer core point P2 Inner core point S Boundary part

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI B29K 105: 24 B29L 30:00

Claims (5)

[Claims] A pneumatic tire manufacturing method for manufacturing a pneumatic tire by inserting a green cover of a tire into a mold and vulcanizing the green cover, wherein the green cover covers a sidewall portion from a tread portion. A carcass locked by the bead core of the bead portion, and a sidewall rubber disposed on the carcass outer surface of the sidewall portion and having a radially inner end connected to a bead chafer for reinforcing the bead seat surface, When the green cover is inserted into the mold, the boundary between the sidewall rubber and the bead chafer is formed on the outer surface of the green cover by the sidewall rubber edge, and the axial line L1 passing through the tire radial outer end of the bead core. In the radial direction outside the core outer point P1 where the outer cover and the raw cover outer surface intersect, or in the axial direction passing through the tire radial inner end of the bead core Core inner point L2 and said raw cover outer surface intersects P
2. A method for manufacturing a pneumatic tire, comprising vulcanizing the green cover at a position radially inward of the green cover. 2. The side wall rubber comprises a side base rubber and a clinch rubber harder than the side base rubber connected to a radial inner end of the side base rubber. 2. The method for producing a pneumatic tire according to 1. 3. The pneumatic tire according to claim 1, wherein the raw cover has a minimum thickness D of a core transverse rubber between an outer surface of the raw cover and the bead core is 2.5 mm or more. Manufacturing method. 4. The raw cover includes a main body extending from a tread portion of a tire cavity surface to a bead portion via a sidewall portion and a bead portion. The raw cover extends from the inside in the tire axial direction to the outside around the bead core and is connected to the main body portion. The method for manufacturing a pneumatic tire according to any one of claims 1 to 3, further comprising an inner liner rubber having a folded portion. 5. The raw cover according to claim 1, wherein the carcass is formed of one carcass ply, and the cord reinforcement of the bead portion is formed of only the carcass cord of the carcass ply. 3. The method for producing a pneumatic tire according to item 1.