JPH07276929A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To prevent the generation of creases on the external wall surface of a side wall caused by the edge of the folded part of a carcass so as to heighten outward appearance while improving durability. CONSTITUTION:The tip of the folded part of the singular carcass ply of a carcass 6, or the tip P of the outer folded part on the tire axial outermost side of the folded parts of plural carcass plies is positioned on the tire equator C side in relation to a radial line N passing the tread edge E and on the radially inner side of a belt layer 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire capable of improving appearance by preventing wrinkles from being generated on the outer wall surface of a sidewall portion due to an end edge of a folded portion of a carcass while maintaining durability. .

[0002]

2. Description of the Related Art In a pneumatic tire used for a large vehicle such as a truck or a bus, a high load acts on the carcass so that the folded portion of the carcass is raised to increase the rigidity of a sidewall portion. The turn-up type is often used.

In order to construct a carcass having such a high turn-up construction, conventionally, as shown in FIGS.
The carcass plies a and a are folded back around the bead core b from the inner side in the tire axial direction to the outer side, and therefore the folded back portion c rises along the outer wall surface e of the sidewall portion d. In a tire under such a high load, a carcass is often formed by stacking a plurality of carcass plies.

[0004]

However, as described above, the folded portion c rises along the outer wall surface f of the sidewall portion d, so that the rubber g forming the outer wall surface f of the sidewall portion d is folded back to the folded portion c. Since a step is formed in the rubber in the thickness direction at the end c1 of the tire, wrinkles h easily occur on the outer wall surface e of the end c1 and the appearance of the tire is deteriorated, and cracks are generated from the wrinkles h as a starting point. Reduce sex.

Moreover, since the outer wall surface e where the folded-back end c1 is located is near the maximum width m of the tire in the high turn-up structure tire, a large tensile stress is generated by the action of the load, and as a result, the wrinkles of the tire are generated. Remarkably reduces strength.

In order to solve one of the above problems, it has been proposed that a wrinkle is prevented by providing a reinforcing filler on the outside of the folded portion of the carcass. However, when a reinforcing filler is provided, The above problems such as the running performance of the tire changing such as the tire longitudinal spring constant changing and the fuel consumption increasing due to the increase in the tire weight have not been solved yet.

Further, as shown in FIGS. 3 and 4, the carcass a
The outer ply j extending from the tread portion to the side wall portion d to the bead portion is arranged on the outward surface e side of the folded portion c, and the step generated by the end portion of the folded portion c of the sidewall portion d is relaxed. Is proposed. However, by providing the outer ply j, wrinkles are reduced, but tire weight is increased and fuel consumption is increased. Further, in such a carcass structure, in order to ensure durability under high load, a reinforcing layer k is further provided on the bead portion.
However, this further increases the weight and lowers the productivity.

As a result of repeated studies to solve the above-mentioned problems, the inventors of the present invention have positioned the tip of the winding portion of the carcass on the tire equator side beyond the radial line passing through the tread edge, and The inventors have found that wrinkles, which tend to occur on the outer wall surface of the sidewall portion, can be eliminated without causing an increase in weight, and that they can be easily manufactured, and completed the present invention.

According to the present invention, the outer wall surface of the side wall portion can be molded without wrinkling without impairing durability,
The purpose of the present invention is to provide a pneumatic tire that can improve appearance and promote weight reduction.

[0010]

SUMMARY OF THE INVENTION The present invention is directed to a single or plural carcass ply having a turn-back portion that returns from a tread portion to a sidewall portion around a bead core of a bead portion from an inner side toward an outer side in a tire axial direction. A pneumatic tire comprising a carcass consisting of and a belt layer consisting of a belt ply which is arranged inside and outside the tread portion and on the outside in the tire radial direction of the carcass, the folding portion of a single carcass ply. Of the carcass ply, or the tip of the outer folded portion on the outermost side in the tire axial direction of the folded portion of the plurality of carcass plies is located on the tire equator side and radially inside the belt layer with respect to the radial line passing through the tread edge. It is a pneumatic tire characterized by that.

The folded portion has a length of 0.05 times or more and 0.20 times or less of the inner belt ply width, which is the width of the inner belt ply in the tire axial direction, and has a radius overlapping with the belt ply. It is preferable to provide the overlapping portion at a position outside the direction.

If the overlap margin is less than 0.05 times, the durability may be insufficient, and even if it exceeds 0.20 times, the durability does not change and the tire weight increases and the cost increases. .

[0013]

The carcass ply forming the carcass has a structure in which the carcass ply is folded back around the bead core from the inner side in the tire axial direction to the outer side, so that the carcass can be easily and easily molded during tire molding.

In the carcass ply, the tip of the folded portion is located inside the radial line passing through the tread edge. As a result, the ply closest to the outer wall surface of the side wall portion is continuous without interruption in the side wall portion, improves the appearance without wrinkling on the outer wall surface, and is the starting point of this wrinkle. It is possible to prevent the occurrence of cracks and improve durability.

Further, it is more preferable that the tip of the folded portion overlaps the belt layer at the inner and outer positions in the radial direction, and an outer carcass arranged outside the carcass ply shown in FIG. 3 is not provided. In addition, since there is no need to provide a filler or the like that covers the folded-back portion and the bead portion, the sidewall portion and the bead portion do not change in rigidity, and thus the running characteristics of the tire do not change. Furthermore, the weight of the tire is not increased.

As described above, according to the present invention, by organically combining and integrating the above-mentioned components, it is possible to prevent the occurrence of wrinkles on the outer wall surface of the sidewall portion while maintaining durability, and to make the tire look good. The tire can be improved and the weight can be reduced, and it can be suitably used as a tire for trucks and buses used at high internal pressure.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, a pneumatic tire 1 has a tread portion 2, a pair of sidewall portions 3 and 3 extending inward in the tire radial direction from both sides thereof, and a bead portion 4 extending inward of the sidewall portion 3.

Further, in the pneumatic tire 1, a folded-back portion 6b is formed by folding back around the bead core 5 from the tread portion 2 to the bead portion 4 through the sidewall portion 3 toward the outer side in the tire axial direction. A carcass 6 including a plurality of carcass plies, and a belt layer 7 including a belt ply arranged outside the carcass 6 and inside the tread portion.

In this embodiment, a bead apex 8 made of hard rubber having a triangular cross section is erected from the bead core 5 in the radial direction and between the main body of the carcass 6 and the folded portion.

In this example, the carcass 6 is composed of two carcass plies 6A and 6B which are arranged inside and outside so that each carcass ply 6A and 6B is made of nylon, polyester, rayon or aromatic polyamide. Carcass cord made of organic fiber such as 7 against tire equatorial plane C
The carcass cords are formed in a radial or semi-radial arrangement in which they are juxtaposed at an angle of 5 to 90 °, and the carcass cords are arranged so as to intersect each other between the carcass plies.

In this embodiment, the belt layer 7 is composed of three belt plies which are arranged inside, inside and outside so that each belt ply is made of organic fiber such as nylon, polyester, rayon, aromatic polyamide or the like. The belt cord made of steel is inclined at an angle of 10 to 70 degrees with respect to the tire equatorial plane C, and the belt plies are arranged so as to intersect with each other to have a hoop effect, thereby increasing the rigidity of the tread portion 2. There is.

In the inner carcass ply 6A, the folded-back portion 6b is interrupted in the vicinity of the maximum width point B of the tire, while the outer carcass ply 6B is provided at the tip P of the folded-back portion, that is, the outer folded-back portion on the outermost side in the tire axial direction. The tip P is located closer to the tire equator C than the radial line N passing through the tread edge E and inside the radius of the belt layer 7. By disposing the tip P at this position, even if the amount of rubber in the buttress portion 3B of the sidewall portion 3 is large and the wall thickness becomes thick, there is no risk of wrinkling due to internal pressure filling by the tip P.

Further, it is preferable that the belt ply 7A in the belt layer 7 is formed with an overlapping portion 10 which is radially overlapped.

In the present embodiment, the overlapping portion 10 has a length L of 0.05 times or more and 0.20 times or less of the inner belt ply width WB which is the width of the inner belt ply 7A in the tire axial direction. There is.

FIG. 2 shows another embodiment. In this example, the carcass 6 is composed of a single carcass ply 6C, and the belt layer 7 is composed of two inner and outer belt plies 7A and 7C.
Formed by.

The carcass ply 6C has a tip P located radially outward of the belt ply 7A within the belt layer 7 on the tire equator C side with respect to the radial line N passing through the tread edge. Thus, the overlapping portion 10 that overlaps the belt ply 7A is formed. As described above, the present invention can be modified into various aspects.

[0027]

SPECIFIC EXAMPLES Tires (Examples 1 to 4 and 11) having tire sizes of 7.00R16 12PR and 6.50R16 8PR and having the configuration shown in FIG. 1 or 2 were prototyped, and their performances were tested. It was For comparison, a tire having a conventional configuration (conventional examples 1 and 1
1) and the tires (Comparative Examples 1 and 11) having configurations other than those of the present application were also tested and their performances were compared.

The test procedure is as follows. 1) Bead durability Using a drum tester, the specified maximum internal pressure was applied to the sample tire,
A peripheral speed of 50km / with a load 1.5 times the specified maximum load
While traveling at h, the traveling distance until damage to the bead portion was measured, and the measured value was used as Conventional Example 1 or Conventional Example 1
The values are represented by indices with 1 being 100. The higher the value, the higher the durability.

2) Appearance of Sidewall Part A new tire was visually evaluated and evaluated by a 5-step method. The larger the value, the better. The test results are shown in Table 1, and the structure of Fila K used in Conventional Example 1 is shown in Table 2.

[0030]

[Table 1]

[0031]

[Table 2]

As a result of the test, each of the examples is a conventional example,
Compared with the comparative example, the wrinkles that tended to occur in the sidewall portion without significantly impairing the bead durability can be significantly reduced, the appearance of the sidewall portion can be improved, and the weight can be reduced compared to the conventional example. I was able to confirm that

[0033]

As described above, the pneumatic tire of the present invention is
The outer wall surface of the sidewall part is the outer wall of the carcass ply, because the tip of the outer folded part of the carcass ply is located on the tire equator side and the radial inner side of the belt layer with respect to the radial line passing through the tread edge. It is possible to prevent the occurrence of wrinkles on the surface, enhance the appearance, and reduce the weight while maintaining the durability.

[Brief description of drawings]

FIG. 1 is a right half sectional view of a tire showing an embodiment of the present invention.

FIG. 2 is a right half sectional view of a tire showing another embodiment.

FIG. 3 is a cross-sectional view showing a conventional tire.

FIG. 4 is a cross-sectional view showing a conventional tire.

FIG. 5 is a cross-sectional view showing a conventional tire.

FIG. 6 is a partial perspective view thereof.

FIG. 7 is a sectional view showing the operation.

[Explanation of symbols]

 2 tread part 3 sidewall part 4 bead part 5 bead core 6 carcass 6A, 6B, 6C carcass ply 6b folded part 7 belt layer 7A, 7B, 7C belt ply 10 overlapping part C tire equator E tread edge L length of overlapping part N Radial direction line P Tip of folded part

Claims (2)

[Claims] 1. A carcass composed of a single or plural carcass plies having a turn-back portion that passes from a tread portion to a sidewall portion and turns around a bead core of a bead portion from an inner side toward an outer side in a tire axial direction, and the tread portion. A pneumatic tire comprising a belt layer made of belt plies that are arranged inside and outside of the carcass on the outside in the tire radial direction of the carcass, the tip of the folded portion of a single carcass ply, or a plurality of carcass plies. The tip of the outer folded portion located on the outermost side in the tire axial direction of the folded portion of the pneumatic tire, which is located on the tire equator side and on the radial inner side of the belt layer with respect to the radial line passing through the tread edge. . 2. The belt ply has a length that is not less than 0.05 times and not more than 0.20 times the inner belt ply width, which is the width of the inner belt ply in the tire axial direction. The pneumatic tire according to claim 1, wherein the pneumatic tire has an overlapping portion that overlaps at a radially outer position.