JP3234646B2 - Manufacturing method for pneumatic tires - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

This invention relates to the manufacture of pneumatic tires.
According to the method, in particular , a concave portion was formed on a sidewall surface.
The present invention relates to a method for manufacturing a pneumatic tire.

[0002]

2. Description of the Related Art Conventionally, as a pneumatic tire having improved durability of a bead portion, for example, British Patent No. 12109
No. 35 is known.

As shown in FIG. 8, this has a carcass ply 16 main body portion 18 on the inside in the axial direction of the bead 12 and extends along the main body portion 18 of the carcass ply 16 on the outside in the axial direction of the bead 12. In the pneumatic tire 100 having the folded portion 20, the folded portion 20
A concave portion 36 is formed on the tire surface radially outwardly away from the radially outer end of the tire. The recesses 36 may be continuous in the circumferential direction, may be provided in large numbers, and may be arranged apart from each other in the circumferential direction.

[0004] The manufacture of a pneumatic tire having a radial structure is as follows.
In general, it begins by winding the carcass component around a cylindrical tire building drum. This carcass component generally comprises an inner liner, a cord reinforcing ply called a carcass ply, and beads at both ends in the axial direction.
In the tire bead portion after vulcanization, a rubber member between the body ply and the folded ply, that is, a member serving as a stiffener member is also included adjacent to the bead.

[0005] In the next stage, both ends of the cord reinforcing ply are folded around the bead and the stiffener is sandwiched.

Next, a band-shaped cushion member and a side tread positioned between the belt and the cord reinforcing ply are wound around the cord reinforcing ply to complete a carcass constituting portion.

[0007] In the next step, the carcass component is formed into an annular shape resembling the form of a vulcanized tire. Next, a belt is wound around the carcass component formed in the toroidal shape, and a top tread is further wound around the carcass component to form a green tire, which is subjected to a vulcanization process.

[0008] In the vulcanization step, the green tire is formed by expanding the bladder and placed in a vulcanization mold.

The vulcanization mold has a convex portion for forming the above-mentioned concave portion 36 on the tire surface. When the bladder inflates and the green tire is pressed by the vulcanization mold, the convex portion is formed. The portion removes (pushes out) the rubber in the bead portion to form a concave portion 36 on the tire surface.

However, according to the conventional technique, the concave portion 36 is not provided.
When the carcass ply 16 of the pneumatic tire 100 before filling with the vulcanized internal pressure is deepened, the carcass ply 16 at the portion 16A facing the concave portion 36 inside the tire (in the direction of the arrow IN).
It becomes convex and a desired carcass line cannot be obtained (see FIG. 8). This is because when the convex of the vulcanization mold removes the rubber in the bead portion, the removed rubber flows and the carcass ply 16
Is pressed, and the pressed portion of the carcass ply 16 is deformed inward of the tire. As described above, when the carcass ply 16 is deformed and the carcass line has a convex portion inside the tire, the convex portion is deformed in a direction in which the convex is eliminated at the time of filling the internal pressure (outward of the tire). For this reason, in the pneumatic tire 100 filled with the internal pressure, bending deformation such that tensile strain occurs occurs on the outer surface of the tire near the convex portion of the carcass line, and so-called ozone cracks are formed on the outer surface of the concave portion. And various durability problems occur, for example, cracks are easily formed due to damage from curbs and the like. For this reason, such a method is not adopted, and even if there is, the concave portion 36 of the pneumatic tire 100 is not used.
Could only be done to a limited depth.

The effect of improving the bead durability by the recess in the pneumatic tire depends on the depth of the recess. The function of this recess is as follows.

Now, it is assumed that a pneumatic tire under a load is running. At this time, since the sidewall portion on the ground side of the pneumatic tire bends by receiving a reaction force from the road surface, a stress is generated inside the sidewall portion, and the internal stress is generated by the outer ply disposed outside the bead in the axial direction. A large compressive strain is generated at the outer end in the radial direction. However, the internal stress generated radially outward is blocked by the concave portion formed on the tire outer surface between the radial outer end of the outer ply and the tire maximum width position, and The effect is reduced.

Here, the region where the internal stress is blocked is a region radially outside of the concave portion and overlaps with the concave portion. Therefore, in order to make the effect of the blocking effective, the depth of the concave portion is increased. This is important. However, due to the above-described problem, the depth of the concave portion cannot be obtained, and a sufficient effect cannot be obtained.

Further, in recent years, the wear life has been extended due to the remarkable improvement in tread rubber, and the number of times of recap rehabilitation of a retread tire has been increasing each time the tread is worn out. Improvement in bead durability is strongly demanded, and the above-mentioned solution is needed.

In consideration of the above facts, the present invention is applied to forming a pneumatic tire capable of preventing the occurrence of ozone cracks in a recess on a sidewall surface and a pneumatic tire having a recess on a sidewall surface. It is an object of the present invention to provide a method of manufacturing a pneumatic tire without deforming a carcass line.

[0016]

In the method of manufacturing a pneumatic tire according to the present invention, a recess having a depth of at least 1/10 of the thickness of the tire is formed on the cured sidewall surface. The method for manufacturing a pneumatic tire is characterized in that an unvulcanized side tread rubber member to be pasted on a cylindrical tire forming drum is provided in advance with a concave portion that matches the concave portion.

[0017]

[0018]

According to the method for manufacturing a pneumatic tire according to the first aspect of the present invention, a pneumatic tire having a recess having a depth of 1/10 or more of the thickness of the tire is formed on the cured sidewall surface. In manufacturing, the unvulcanized side tread rubber member to be stuck on the cylindrical tire building drum is provided in advance with a concave portion that matches the concave portion. For this reason, when the green tire having the depression in the side tread rubber is loaded in the vulcanization mold, the depression is aligned with the projection of the vulcanization mold that forms the recess, so that the local tire is pushed away by the projection. Since the flow of the rubber amount is small, the ply cord is hardly pushed into the tire, and the carcass line is not substantially deformed.

Further, the pneumatic tire according to claim 1 is manufactured.
The pneumatic tire manufactured by the manufacturing method has substantially no deformed portion in the carcass line, and when the internal pressure is filled, bending deformation such that tensile strain occurs on the tire outer surface of the concave portion does not occur, and the concave portion of the concave portion Ozone cracks on the outer surface of the tire can be prevented from occurring.

[0020]

【Example】

[First Embodiment] A first embodiment of the present invention will be described with reference to FIGS.

As shown in FIG. 1, the pneumatic tire 10 of this embodiment has a pair of beads 12 and a carcass 14 having a toroidal shape. The carcass 14 has a carcass 14 therein in a radial direction (meridian direction). It is composed of at least one carcass ply 16 in which a number of extending cords are embedded.

As shown in FIGS. 1 and 2, the carcass ply 16 extends from one bead 12 to the other bead 12, so that the carcass ply 16 has a main body portion 18 located inside the bead 12 in the axial direction, and And a folded portion 20 which is folded outward and is located outside the bead 12 in the axial direction. A stiffener 19 is provided in a substantially triangular area formed between the main body 18 and the folded portion 20.

As shown in FIG. 1, a belt 24 composed of at least two belt plies 22 is disposed radially outward of the carcass 14, and inside these belt plies 22, the belt 24 is inclined with respect to the circumferential direction. Numerous reinforcing cords are embedded, and these reinforcing cords cross each other at adjacent belt plies 22.

A top tread 28 having a groove 26 such as a main groove or a lateral groove formed radially outside the belt 24.
However, side treads 34 are arranged on both outer sides in the axial direction of the carcass 14, respectively. The thickness of the side tread 34 is gradually reduced near both ends in the width direction, and one end is disposed near the end of the belt 24, and the other end is a bead of the folded portion 20. 1
It is arranged on the side opposite to the two sides.

In general, when the pneumatic tire is run while applying a load, the sidewall portion on the ground side of the pneumatic tire is bent by receiving a reaction force from the road surface, and as a result, a stress is generated inside the bent portion. This internal stress causes a large compressive strain at the radially outer end of the folded portion of the carcass ply. In the pneumatic tire 10 of the present embodiment, since the concave portion 36 is formed on the tire outer surface between the radially outer end 32 of the folded portion 20 and the tire maximum width position M, the concave portion 36 is formed radially outside. The transmission of the generated internal stress to the folded portion 20 can be blocked, and the compressive strain generated in the folded portion 20 is reduced. For this reason, the pneumatic tire 10 of the present embodiment
The separation of the carcass ply in the vicinity of the folded portion 20 is prevented, and the durability of the bead portion is improved.

In this embodiment, the concave portion 36 is an annular groove extending continuously in the circumferential direction, but may be divided into a plurality in the circumferential direction.

FIG. 3 shows a pneumatic tire 10 according to this embodiment.
A part of the unvulcanized side tread 34 used for the production of the green tire is shown. The unvulcanized side tread 34 is formed in a long strip shape, and the thickness dimension in the width direction is substantially changed.

FIG. 4 shows a portion of a conventional unvulcanized side tread 102. As shown in the drawing, the side tread 102 gradually decreases in thickness in the vicinity of both ends in the width direction, and has a bulging portion 1 on the side that is located radially outward after vulcanization from the center in the width direction.
04. The reason why this portion is thick is that the carcass component including the side tread on the cylindrical tire building drum is formed in an annular shape similar to the shape of a vulcanized tire as described above. This is because, at this time, the expansion of the diameter of the raised portion 104 is larger than the expansion of a portion that is located radially inward after vulcanization. Then, the wall thickness gradually decreases from the raised portion 104 to a portion 106 which is located radially inward after vulcanization and is located near the folded end portion of the carcass ply. Is consistently uniform.

On the other hand, as shown in FIG. 3, the unvulcanized side tread 34 of the present embodiment is located on the other side in the width direction of the folded portion of the carcass ply. A concave portion 40 is formed in a middle portion between the center portion in the width direction, which is a portion corresponding to the maximum width position M, and the other end, and small arc-shaped convex portions 4 are formed on both sides of the concave portion 40.
2A and the convex portion 44B are formed, and the thickness dimension in the width direction is substantially changed.

The protrusions 42A and the protrusions 4 are provided on both sides of the recess 40.
The reason for forming 4B is that the rubber capacity of the unvulcanized side tread 34 of the present embodiment is reduced by the conventional uncured side tread 1
02 is equivalent to the rubber capacity of the convex portion 42A and the convex portion 44B.
To compensate for this. Therefore, when the unvulcanized side tread 34 of the present embodiment is compared with the conventional unvulcanized side tread 102, the rubber capacity as the side tread is substantially equal, in other words, the cut when cut in the width direction. The areas are almost equal.

That is, as shown in FIG. 5, when comparing the cross-sectional shapes of the unvulcanized side tread 34 of this embodiment and the conventional unvulcanized side tread 102, Convex portion 42A and convex portion 44 of side tread 34
The heights of the top A and the long part B of B are HA and HB, respectively.
The portions of the conventional unvulcanized side tread 102 corresponding to the width direction positions of the tops of the protrusions 42A and 44B are defined as points a and b, respectively, and the heights of the points a and b are defined as ha, respectively. , Hb, HA and HB are larger than ha and hb. In this embodiment, HA and H
B have almost the same dimensions.

Also, from the deepest part of the concave part 40 to the convex part 42A
And the difference dimension d up to the top of the convex portion 44B (or the average position of the convex portion 44A and the convex portion 44B when the height of the convex portion 44B is different).
As shown in FIG. 2, the depth D of the recess 36 of the vulcanized pneumatic tire 10 from the tire outer surface is 20
% Or more and 100% or less, and is set to 40% in this embodiment.

The side tread 34 and predetermined tire components (inner liner (not shown), carcass ply 16, bead 12, stiffener 19, cushion member (not shown), belt ply 22, top tread 28, etc. (The rubber member is also in an unvulcanized state.) The green tire assembled through a predetermined green tire forming step using (1) is loaded into a predetermined vulcanization mold, and a bladder (not shown) in the vulcanization mold is expanded. Then, the green tire is pressed against the inner surface of the vulcanizing mold. At this time, since the concave portion 40 of the side tread 34 is aligned with the convex portion of the vulcanizing mold, the local rubber amount pushed away by the convex portion of the vulcanizing mold is small. That is, in this embodiment, since the local rubber flow for pushing the carcass ply 16 into the tire at the time of vulcanization molding is small, the carcass line facing the recess 40 may not be deformed to the tire inside. Almost, the carcass line inside the concave portion 36 of the vulcanized pneumatic tire 10 inside the tire has an appropriate shape with substantially no deformed portion.

As described above, the pneumatic tire 10 of the present embodiment vulcanized and formed by using the unvulcanized side tread 34 having the concave portion 40 has a convex inside the tire inside the concave portion 36. Since the deformed portion of the carcass line does not substantially occur, no tensile strain is generated on the rubber surface of the concave portion 36 by filling the internal pressure unlike the conventional tire. Therefore, the pneumatic tire 10 of the present embodiment
Occurrence of ozone cracks on the rubber surface of the concave portion 36 can be effectively prevented, and cracks, which are likely to be caused by trauma from curbs or the like, can be prevented, thereby improving durability.

It should be noted that from the deepest part of the concave part 40 to the convex part 42A
When the difference d from the top of the protrusion 44B to the top is 20% or less with respect to the depth D of the recess 36 from the tire outer surface, the amount of rubber that the vulcanization-type protrusion forming the recess 36 pushes away is small. It is not preferable because the carcass line may be deformed due to the flow of the rubber.

The shape of the recess 40 is desirably as close as possible to the recess 36, but the shape of the recess 40 is not particularly limited as long as the flow of rubber during vulcanization is small.

[Second Embodiment] FIG. 6 shows a second embodiment of the present invention.
And FIG.

The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

As shown in FIG. 7, in the pneumatic tire 10 of the present embodiment, the depth D of the recess 36 from the outer surface of the tire is made deeper than that of the pneumatic tire 10 of the first embodiment. In the present embodiment, by increasing the depth dimension D of the concave portion 36, it is necessary to prevent the side tread 34 from being divided or the thickness of the side tread 34 from becoming extremely thin in order to prevent inconveniences. The vulcanized stiffener 19 is provided with a depression 21 at a position corresponding to the depression 40 of the unvulcanized side tread 34 in advance (FIGS. 6A and 7).
reference).

As shown in FIG. 6B, in the conventional stiffener 119, the side tread contact surface 121 (see FIG. 8) from the portion 119B in contact with the folded end to the radially outer end 119A has a widthwise direction. Although the stiffener 19 in the present embodiment has an arcuate shape with a convex cross section, the unvulcanized stiffener 19 of this embodiment has a side tread contact surface 21 extending from a portion 19A in contact with the radial outer end 32 to a tire radial outer end 19B. (See FIG. 7) is an arc-shaped recess 21 that is concave in the cross section in the width direction.

As a result, it is possible to increase the depth dimension D of the concave portion 36 without dividing the side tread 34 into two parts or forming a partially thin portion. As shown in FIG. The depth D of the recess 36 can be made larger than the thickness T of the recess 36.

The pneumatic tire 10 of the present embodiment has a larger depth of the concave portion 36 than the pneumatic tire 10 of the first embodiment, so that the internal stress acting on the radially outer end 32 of the folded portion 20 is cut off. The effect is great.

[0043]

The method of manufacturing a pneumatic tire according to the first aspect is as described above, so that when forming a tire having a concave portion formed on the side wall surface, the carcass line is substantially deformed. There is no effect. Ma
The method for manufacturing a pneumatic tire according to claim 1
The formed pneumatic tire has a recess when filled with internal pressure.
No tensile strain occurs on the surface of the
It has an excellent effect that generation of a rack is prevented.

[Brief description of the drawings]

FIG. 1 is a meridional sectional view showing a pneumatic tire according to a first embodiment of the present invention.

FIG. 2 is an enlarged sectional view showing the vicinity of an outer ply of the pneumatic tire shown in FIG.

FIG. 3 is a perspective view of a side tread used for the pneumatic tire shown in FIG.

FIG. 4 is a perspective view of a side tread used for a conventional pneumatic tire.

FIG. 5 is a diagram comparing the cross-sectional shapes of a side tread used for a conventional pneumatic tire and a side tread used for a pneumatic tire according to the first embodiment of the present invention.

FIG. 6A is a perspective view of a stiffener used for a tire according to a second embodiment of the present invention, and FIG. 6B is a perspective view of a stiffener used for a conventional tire.

FIG. 7 is a sectional view similar to FIG. 2, showing a tire according to a second embodiment of the present invention.

FIG. 8 is a sectional view similar to FIG. 2, showing a conventional tire.

[Explanation of symbols]

 Reference Signs List 10 Pneumatic tire 34 Side tread 36 Depression 40 Depression

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI // B29K 21:00 B29K 21:00 105: 24 105: 24 B29L 30:00 B29L 30:00 (58) Fields surveyed (Int .Cl. ⁷ , DB name) B29D 30/00-30/72 B29C 33/00-33/76 B60C 13/00-13/04

Claims (1)

(57) [Claims] 1. A method for manufacturing a pneumatic tire in which a recess having a depth of 1/10 or more of the thickness of a tire is formed on the surface of a cured sidewall, the method is applied to a cylindrical tire forming drum. A method for manufacturing a pneumatic tire, characterized in that an unvulcanized side tread rubber member is provided with a depression portion in advance so as to match the concave portion.