JP3367895B2 - Manufacturing method of pneumatic tire - Google Patents

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, which is capable of suitably preventing a bare from being generated near a sidewall rubber edge.

[0002]

2. Description of the Related Art In recent years,
Tires for passenger cars centering on sedans are strongly required to improve quietness (noise performance) and riding comfort during driving. In recent years, in order to improve noise performance and riding comfort, in radial tires for passenger cars, the carcass consists of a single carcass ply, and the cord reinforcement that was placed separately from the carcass in the bead part. Fillerless is used to reduce the rigidity of the bead part by reducing the number of layers.

However, it has been surprisingly found that when such a tire is produced, the rate of occurrence of bears at the bead portion becomes higher than that of conventional tires. The term "bear" refers to a problem in which when the raw cover of a tire is vulcanized with a mold, air between the raw cover and the mold remains and a dent or the like is formed on the surface of the vulcanized tire.

The inventors of the present invention have conducted extensive studies to reduce the occurrence of such a bear, and as shown in FIG. 7, most of the bear c at the bead portion b is a tire having a sidewall rubber a. Concentration occurs in the vicinity of the edge e radially inward, and as shown in FIG. 8, in the raw cover t of the tire inserted into the mold m, the edge e of the sidewall rubber a is both Since the axial line passing through the inner and outer ends of the very hard bead core f made of a substantially non-stretchable material is between the positions fd and fu where the outer surface of the raw cover intersects, the bead core f and the mold m are It was found that they were firmly sandwiched from both sides in the axial direction.

Prescribed markings or the like are applied to the outer surface of the bead portion of the raw cover t of the tire before vulcanization, and the deformed state of the marking is measured after vulcanization to quantify the complicated behavior of the rubber during vulcanization. I tried an experiment to grasp it. From the result shown in FIG. 9, a very large compressive force is applied to the region (between fu and fd) sandwiched between the bead core f and the mold m, and the large compressive force during the vulcanization causes the sidewall. It was found that the abnormal deformation of the rubber edge e was the cause of the bare.

In addition, as described above, due to the monoplying and the fillerless structure, the raw cover t is further reduced in the rubber thickness D between the outer surface g of the raw cover and the bead core f, and the vulcanization of this portion is performed. The fact that the cushioning function in the inside has deteriorated has also been found to further contribute to the generation of bears.

In the present invention, in the state where the green cover is inserted into the mold, the sidewall rubber edge is displaced from between the bead core and the mold to the inside or outside of the tire radial direction to vulcanize the green cover. Based on the above, it is an object of the present invention to provide a method for manufacturing a pneumatic tire capable of suitably preventing the occurrence of the above-mentioned bear.

Further , by limiting the minimum thickness D of the lateral rubber between the outer surface of the green cover and the bead core to a predetermined value or more, it is possible to further effectively prevent the generation of the bare tire. It is intended to provide a manufacturing method.

According to the third aspect of the present invention, when the thickness D of the core transverse rubber is increased, it is possible to provide a method for manufacturing a pneumatic tire that prevents an increase in the number of parts and the like and does not impair productivity. Has an aim.

Further, in the invention according to claim 4 , a pneumatic tire capable of improving noise performance and riding comfort by making it monoply and fillerless can preferably prevent the generation of the bare. Is intended to provide.

[0011]

According to a first aspect of the present invention, the method for producing a pneumatic tire comprises producing a pneumatic tire by inserting a raw tire cover into a mold and performing vulcanization molding. The raw cover is disposed on the carcass outer surface of the sidewall portion and the carcass locked by the bead core of the bead portion from the tread portion through the sidewall portion, and the inner end in the radial direction reinforces the bead seat surface. And a sidewall rubber connected to the bead chafer, and in a state where the green cover is inserted into a mold, a sidewall rubber edge in which a boundary portion between the sidewall rubber and the bead chafer appears on the outer surface of the green cover. Is the outer side in the radial direction from the core outer point P1 where the axial line L1 passing through the outer end of the bead core in the tire radial direction and the outer surface of the raw cover intersect. Alternatively, the raw cover is vulcanized by being positioned radially inward of a core inner point P2 where the axial line L2 passing through the tire radial inner end of the bead core and the raw cover outer surface intersect. It is a tire manufacturing method.

The invention according to claim 1 is the green cover.
Is a core lateral rubber between the outer surface of the green cover and the bead core.
Has a minimum thickness D of 2.5 mm or more.

According to a second aspect of the present invention, the side window is
The rubber is a side base rubber and this side base rubber.
Of the side base body connected to the inner end of the tire in the radial direction of the tire.
It is made of clinch rubber that is harder than rubber.
It

According to a third aspect of the present invention, the raw cover includes a main body portion extending from the tread portion of the inner surface of the tire to the bead portion through the sidewall portion, and a body portion connected to the main body portion around the bead core. The method for producing a pneumatic tire according to any one of claims 1 to 3, further comprising an inner liner rubber having a folded-back portion that is folded back from the inner side in the tire axial direction.

The invention according to claim 4 is characterized in that, in the green cover, the carcass is composed of one carcass ply, and the cord reinforcement of the bead portion is composed only of the carcass cord of the carcass ply. The method for producing a pneumatic tire according to any one of 1 to 4.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION An 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 the green cover 2 of the pneumatic tire is inserted into the mold 3 and vulcanized and molded. In the present embodiment, the raw cover 2 includes, as shown in FIG. 1, a carcass 9 engaged with a bead core 7 of a bead portion 6 from a tread portion 4 through a sidewall portion 5, a carcass 9 inside the tread portion and a radius of the carcass 9. And a belt layer 10 disposed outside in the direction.

In the present embodiment, the carcass 9 is formed of a single carcass ply 9A that is folded back and locked from the axially inner side to the outer side so as to wrap the bead apex rubber 8 around the bead core 7. 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 the present embodiment, the belt cords are arranged at a small angle of 10 to 40 ° with respect to the tire equator, and the outer two belt plies 10A and 10B intersect each other. It is constructed by stacking in the direction. As the belt cord, a steel cord is used in this example, but a highly elastic organic fiber cord such as aramid or rayon can also be used if necessary.

The raw cover 2 is made of a tread rubber 11
, Sidewall rubber 12, and bead chafer 13
And have. The tread rubber 11 is the belt layer 1
0 is arranged outside, and a predetermined tread pattern is engraved by the tread molding die 3a.

The sidewall rubber 12 is arranged on the outer surface of the carcass 9 of the sidewall portion 5, the tire radial outer end is connected to the tread rubber 11, and the radial inner end is the bead chafer 13. Connected to. The side wall rubber 12 is a harder and smaller length than the side base rubber 12a that occupies most of the side wall portion 5 and the side base rubber 12a connected to the inner end of the side base rubber 12a in the tire radial direction. The one made of two kinds of rubber such as the clinch rubber 12b is illustrated.

In the present embodiment, the bead chafer 13 is, as shown in an enlarged view in FIG. 2, a base portion 13a extending on the bead seat surface 14 and an inner end of the base portion 13a which extends axially outward from both axial ends of the base portion 13a. Outside startup section 13
A hard rubber portion 13A having i and 13o, and a rubber-coated canvas portion 13B that wraps the hard rubber portion 13A from the outside. Bead chafer 13
Is provided on the bead portion 6 prior to the attachment of the sidewall rubber 12, and the hard rubber portion 13A is
By vulcanization, it becomes harder than the clinch rubber 12b.
The bead chafer 13 can protect the bead seat surface 14 after the rim assembly and ensure its rigidity.

Further, in the raw cover 2 of this embodiment, the carcass 9 is composed of one carcass ply 9A, and the cord reinforcement of the bead portion 6 is composed only of the carcass cord of the carcass ply 9A. Therefore, by vulcanizing and molding the raw cover 2, a pneumatic tire having improved noise performance and riding comfort can be obtained.

Although various types of molds can be adopted as the mold 3, in the present embodiment, a tread molding mold 3a capable of molding a tread pattern on the tread rubber 11 and a sidewall portion 5 and a bead arranged on both sides thereof. The part 6 is formed and has an upper mold 3b and a lower mold 3c that can be separated from each other.

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

As a result, in the present embodiment, it is possible to prevent a large compressive force from acting on the sidewall rubber edge E during vulcanization and suppress its abnormal deformation, and in the pneumatic tire in which monoply and fillerless are used, It is possible to effectively suppress the occurrence of bare near the wall rubber edge E. Here, the state in which the green cover 2 is inserted into the mold 3 refers to a state in which the respective molds 3a to 3c of the mold 3 are closed. This is done by using a plaster piece having the same molding surface as the mold. It is possible to confirm.

Further, in the present invention, it is important to specify the position of the sidewall rubber edge E in the state where the green cover 2 is inserted into the mold 3, and where the sidewall rubber edge E is in the finished tire after vulcanization. Whether it is located does not matter so much from the standpoint of preventing bears. The sidewall rubber edge E changes its position in the radial direction of the tire before and after vulcanization. Therefore, in the finished tire after vulcanization manufactured by the method of the present invention, the sidewall rubber edge E is located outside the core P1 and inside the core. It may be located between the direction P2 and the direction P2.

In the present embodiment, as shown in FIG. 2, the clinch rubber 12b of the sidewall rubber 12 is formed in a tapered shape in which the thickness gradually decreases toward the sidewall rubber edge E, and the canvas portion of the bead chafer 13 is formed. Thirteen
An example is shown in which the side wall rubber edge E is connected to the outer surface of B and is located radially outside the core outer point P1. Such positioning of the side wall rubber edge E is performed by sticking the side wall rubber 12 and the side wall rubber 1 at the time of molding the raw cover.
It can be easily made by adjusting the width dimension of 2 and the like.

In the case of this example, 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 is set. However, it is preferably 0.5 mm or more, more preferably 1.0 mm or more, and further preferably 1.5 mm or more. If the height h1 is too large, the clinch rubber 12b may not sufficiently contact the rim in the finished tire, and there is a possibility that the rim may be displaced. Therefore, the upper limit of each value is preferably 5.0 mm.

Further, while the green cover 2 is made monoply and fillerless, the minimum thickness D of the core lateral rubber 15 between the green cover outer surface 2a and the bead core 7 (FIG. 2).
(Shown in FIG. 4) is secured to 2.5 mm or more.

Generally, when the raw cover 2 is made into a mono-ply or filler-less one, the core lateral rubber 15 tends to be thin. For example, in the case of a radial tire for passenger cars, the minimum thickness D of the core lateral rubber 15 is small. Approximately 1.9 to 2.0 mm
However, the cushioning effect in this part tends to decrease. Then, the inventor of the present invention has found out that as the result of various experiments, if the cushioning effect of the core lateral rubber 15 is reduced, bare is likely to occur.

Therefore, the outer surface 2a of the raw cover and the bead core 7
By limiting the minimum thickness D of the lateral core rubber 15 between and to 2.5 mm or more, the cushioning 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, more preferably 2.5 to 2.9 mm.
Is particularly desirable.

In the present embodiment, in order to increase the minimum thickness D of the core lateral rubber 15, a main body portion 16a which is arranged on the inner surface of the tire and extends from the tread portion 4 to the bead portion 6 via the sidewall portion 5 is formed. The inner liner rubber 16 is provided integrally with the main body portion 16a and has a folded portion 16b that is folded around the bead core 7 from the inner side to the outer side in the tire axial direction. In this way, the folded portion 16b of the inner liner rubber is attached to the core lateral rubber 1
5, the core lateral rubber 15 has a thickness D
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 includes a base portion 13a extending over the bead seat surface 14, and a hard rubber portion 13A having only a rising portion 13i that rises from the inner side in the axial direction of the base portion 13a to the outer side in the tire radial direction, and A rubber-coated canvas portion 13B that wraps the hard rubber portion 13A from the outside.

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

Further, FIG. 4 shows another embodiment of the raw cover 2. In this example, the bead chafer 13 is
A base portion 13a extending on the bead seat surface 14 and the base portion 1
A hard rubber portion 13A having inner and outer rising portions 13i and 13o rising from the inner and outer ends in the axial direction of 3a to the outer side in the radial direction of the tire, and a rubber-coated canvas portion 13B that wraps the rubber portion 13A from the outside. Composed of and. Further, the clinch rubber 12b of the sidewall rubber 12 is
In this example, the bead seat surface 14 is also illustrated.

The embodiments of the present invention have been described in detail above. For example, the sidewall rubber 12 is formed by connecting three or more kinds of rubber in the tire radial direction, and the bead chafer 13 is made of only hard rubber. The raw cover may further include a plurality of carcass plies or bead reinforcing layers, and the present invention may be modified in various forms.

[0037]

Example A raw cover of a tire having a finished size of 175 / 70R13 was prototyped and the effect of the production method of the present invention was tested. The test was carried out by vulcanizing tires (comparative examples 1 and 2) in which the sidewall rubber edge of the green cover was positioned between the core outer point P1 and the inner point P2 in a state of being inserted into the mold, and a metal mold. With the side cover rubber edge of the green cover inserted in the mold, the core outer point P1 and inner core point P1
The tire which was vulcanized and molded by removing it from between 2 and 1 (Example 1,
2) , a tire having D of 1.9 mm (Comparative Example 3,
Regarding 4) , the occurrence rate of bare (n = 200) near the sidewall rubber edge 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 bare in the example was reduced as compared with the comparative example, and at the same time, when 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. Further, the results of examining the forces acting on the bead portion during vulcanization in Examples 2 and 4 are shown in FIGS. 5 and 6. As is clear from the figure, it can be confirmed that the sidewall rubber edge E is not subjected to a large compressive force.

[0040]

As described above, according to the first aspect of the invention, the sidewall rubber edge is located radially outside the core outer point P1 or in the core inner point in the state where the green cover is inserted into the mold. By vulcanizing the green cover by locating it radially inward of P2, it is possible to prevent a large compressive force from acting on the edge of the sidewall rubber during vulcanization, and to suppress its abnormal deformation. Because you can
It is possible to effectively suppress the generation of bears near this edge.

Further , the raw cover can exert a cushion function in this portion during vulcanization by limiting the minimum thickness D of the core lateral rubber between the outer surface of the raw cover and the bead core to 2.5 mm or more, Furthermore, the effect of suppressing bears can be enhanced.

According to the third aspect of the present invention, the inner liner rubber disposed on the inner surface of the tire is folded back from the inner side to the outer side in the tire axial direction around the bead core, thereby increasing the number of parts without causing an increase in the number of parts. It can help to increase the thickness of the cross rubber.

In the invention according to claim 4 , the raw cover is made of one carcass ply, and the cord reinforcement of the bead portion is made only of the carcass cord of the carcass ply, so that noise performance and riding comfort are improved. It is possible to manufacture a pneumatic tire while suppressing the bear of the bead portion.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a state where a green 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 the bead portion of the 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 the force acting on the bead portion (Example 4) during vulcanization.

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

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

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

[Explanation of symbols]

2 raw cover 2a Raw cover outer surface 3 mold 4 tread section 5 Side wall 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 Inner liner rubber body 16b Inner liner rubber folded part E Sidewall rubber edge P1 core outer point P2 core inward point S boundary

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP 10-44720 (JP, A) JP 4-208443 (JP, A) JP 8-66976 (JP, A) JP 3- 243405 (JP, A) JP 5-254315 (JP, A) JP 8-11510 (JP, A) JP 10-66976 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B29D 30/00-30/72 B60C 15 / 00,15 / 06

Claims (4)

(57) [Claims] 1. A method of manufacturing a pneumatic tire, comprising manufacturing a pneumatic tire by inserting a raw tire cover into a mold and performing vulcanization molding, wherein the raw cover includes a tread portion and a sidewall portion. A carcass that is locked by a bead core of a bead portion, and a sidewall rubber that is arranged on the outer surface of the carcass of the sidewall portion and has a radially inner end connected to a bead chafer that reinforces the bead seat surface, Further, in a state where the green cover is inserted into the mold, the sidewall rubber edge where the boundary between the sidewall rubber and the bead chafer appears on the outer surface of the green cover is the axial line L1 passing through the tire radial outer end of the bead core. In the axial direction passing through the outer side in the radial direction from the core outer point P1 where the outer surface of the raw cover intersects, or the inner end in the radial direction of the tire of the bead core. Core inner point L2 and said raw cover outer surface intersects P
The green cover is positioned on the inner side in the radial direction of 2 to vulcanize the green cover, and the green cover is formed between the outer surface of the green cover and the bead core.
A method for manufacturing a pneumatic tire, characterized in that the minimum thickness D of the core transverse rubber is set to 2.5 mm or more . 2. The side wall rubber comprises a side base rubber and a clinch rubber which is harder than the side base rubber and is connected to an inner end of the side base rubber in the tire radial direction. 1. The method for manufacturing the pneumatic tire according to 1. 3. The tread on the inner surface of the tire is the raw cover.
From the base to the bead via the sidewall
And a tie around the bead core that is connected to the body.
With a folded-back portion that is folded back from the inside in the axial direction
An inner liner rubber according to claim 1,
The method for producing a pneumatic tire according to 1 or 2 . 4. The raw cover is a carcass with one carcass.
The splice is used and the cord reinforcement at the bead is
Characterized by consisting only of the carcass cord of the carcass ply
The method for producing the pneumatic tire according to claim 1, wherein