JP2000127719A - Pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic radial tire to suppress the occurrence of bead burst occasioned by heat generation during running in a summer season. SOLUTION: This tire is provided with a tire bead part 2 having an abrasion rubber 7 stretching radially externally of a tire. A carcass 8 is provided with a folded part 9 having an end part rolled up, at the periphery of a bead core 5 embedded in the tire bead part 2, from the inside of the tire toward the outside of the tire. A reinforcing layer 10 is arranged on the outer periphery of the end part of the carcass 8 containing the folded part 9. In this case, provided the rolling-up height H1 of the folded part 9 of the carcass 8 is H1, the rubber thickness of the abrasion rubber 7 in the vicinity of the winding end of the folded part 9 is T, a shortmost distance from the rolling-up end of the folded part 9 to the outer surface of a side wall is L, and a vertical height H from the base of the tire bead part 2 to a tire maximum width is H, setting is effected within a range of H1>0.40H, T<0.04H, and L<0.07H.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire, and more particularly to a pneumatic radial tire for heavy loads such as trucks and buses, in which the durability of a tire bead portion is improved.

[0002]

2. Description of the Related Art Japanese Patent Laid-Open Publication No. Sho 50-1 discloses a conventional technique for improving the durability of a tire bead portion of a pneumatic radial tire.
No. 17102, JP-A-55-106806,
The technology of Japanese Patent Application Laid-Open No. 9-286211 has been proposed.

[0003]

The basic technology for improving the durability of a tire bead portion of a pneumatic radial tire is to provide the tire bead portion with an abrasion rubber extending radially outward and burying the tire bead portion in the tire bead portion. A carcass having a folded portion whose end is wound from the tire inside toward the tire outside around the bead core,
It is to arrange a reinforcing layer on the outer periphery of the end portion of the carcass including the folded portion, suppression of excessive distortion generated around the bead core, such as centrifugal force caused by steering operation during rolling under the load of the tire The purpose of the present invention is to prevent damage such as bead burst due to excessive bending deformation or the like caused by the generation of a lateral force.

However, under running conditions such as when the temperature of the road surface is high, such as in the summer, despite the fact that damage such as a bead burst due to heat generation (temperature rise) of the tire is liable to occur, this temperature is high. There was no technology to improve the durability of the tire bead by taking measures. In order to evaluate the durability performance of the tire bead portion, the present invention considers running in the summer and performs a drum test in a heated state, so that a bead burst (tire rupture) caused by heat generation of the tire can be obtained. He succeeded in developing pneumatic radial tires with reduced damage.

[0005]

According to the present invention, a tire bead portion 2 is provided with an abrasion rubber 7 extended radially outward in a tire radial direction, and an end portion of the tire bead 5 around a bead core 5 embedded in the tire bead portion 2 is provided. Carcass 8 having folded portion 9 wound from the inside toward the outside of the tire
In the pneumatic radial tire in which the reinforcing layer 10 is disposed on the outer periphery of the end portion of the carcass 8 including the folded portion 9, in order to suppress damage such as bead burst caused by heat generation of the tire, Technical measures were taken.

That is, in the present invention according to claim 1, the winding height of the folded portion 9 in the carcass 8 is H1, the rubber thickness of the abrasion rubber 7 near the winding end of the folded portion 9 is T, Folding part 9
When the shortest distance from the winding end of the tire to the outer surface of the sidewall is L, and the vertical height from the base of the tire bead portion 2 to the maximum width of the tire is H, H1> 0.40H and T <0.
04H, L <0.07H.

Further, in the present invention according to claim 2,
2. The carcass 8 according to claim 1, wherein the reinforcing layer 10 is disposed around the end of the carcass 8 including the turn-back portion 9 and the reinforcing portion 10A of the reinforcing layer 10 inside the tire.
Another inner reinforcing layer 11 is interposed between the tire bead portion 2 and a portion 8A inside the tire.

Further, in the present invention according to claim 3,
In the above-mentioned claim 1, the winding height H2 of the reinforcing layer 10 is set lower than the winding height H1 of the folded portion 9. Further, in the present invention according to claim 4, in claim 2 described above, the vertical height position H3 of the another inner reinforcing layer 11 up to the radially outer end is determined by the winding height H1 of the folded portion 9 and It is characterized in that it is set radially outward with respect to the winding height H2 of the reinforcing layer 10.

As a result of the drum test, it has been clarified that the thus constructed pneumatic radial tire according to the present invention has a significantly improved tire life as compared with the comparative tire.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a tire bead portion 2 and a sidewall 3 in a pneumatic radial tire 1.
In the tire bead portion 2 fitted to the rim 4, a ring-shaped bead core 5 having a hexagonal cross section is embedded, and the bead core 5 is provided with a bead filler rubber 6, The tire bead portion 2 is provided with an abrasion rubber 7 extending outward in the tire radial direction.

Around the bead core 5, an end of a one-ply radially arranged carcass 8 made of a metal (steel) cord or the like is formed as a folded portion 9 wound up from the tire inner side to the tire outer side. Yes,
A cross section U is provided around the end of the carcass 8 including the folded portion 9.
A character-shaped reinforcing layer 10 is arranged. If the pneumatic radial tire 1 shown in FIG. 1 is defined as a normal type (normal type), FIG. 2 shows that the inner reinforcing layer 11 different from the reinforcing layer 10 described above is formed by the reinforcing portion 10A of the reinforcing layer 10 and the carcass 8. It is a reinforced type (reinforced type) interposed between the tire bead portion 2 and a portion 8A inside the tire, and other configurations are common to FIG.

A drum test is performed to evaluate the durability of the tire bead portion 2. When the normal type is set to 100 (index), the durability of the tire bead 2 is 130. The present inventor performed a drum test in a heated state in consideration of running in summer, and found that the durability when heating was not performed in a normal type was set to 100 (index) and the durability was reduced to a level of 10 when heating was performed. I knew I was doing it.

[0013] Similarly, when a drum test was performed on the reinforced type, the durability when not heated was 130 (index), and it was found that the durability was reduced to a level of 10 when heated. From this, it can be seen that the durability index is the same level in the drum test in the heated state for both the normal type (FIG. 1) and the reinforced type (FIG. 2).

Based on these findings, the carcass winding height H1 (mm), the vertical height H (mm) from the base to the maximum width of the tire, and the rubber thickness T of the abrasion rubber near the winding end of the folded portion are shown. (Mm), the shortest distance L from the winding end of the folded portion to the outer surface of the sidewall
(Mm), the height of the reinforcement layer H2 (mm), and the height of another reinforcement layer as H3 (mm), these were variously changed, and a durability test (drum test in a heated state) was performed. It is shown in Table 1.

[0015]

[Table 1]

The test tire is 1000R20,
The tire internal pressure (kg / cm ² ) was set to 9.5 for 8.0 and 96 hours, 10.0 for 192 hours, and the tire load (k).
g) are 6000, 6890, and 7800, respectively.
The running speed is 20 km / H. As is apparent from Table 1, when the tire life (evaluation) in the heated state is 10 (index) in Comparative Example 4, the tire life is 15 (index) in the example of the present invention, and a bead burst or the like is obtained. It can be understood that was suppressed.

In FIGS. 1 and 2, the winding height H2 of the reinforcing layer 10 is set lower than the winding height H1 of the folded portion 9. In FIG. The vertical height position H3 up to the radially outer end of 11 is set radially outward with respect to the winding height H1 of the folded-back portion 9 and the winding height H2 of the reinforcing layer 10, and the reinforcing type When a similar test was conducted for, the same results as in Table 1 were obtained.

[0018]

As described above in detail, according to the present invention, a pneumatic radial tire capable of suppressing a bead burst caused by heat generation during running in summer can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view of a normal type bead portion.

FIG. 2 is a sectional view of a reinforced type bead portion.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Radial tire 2 Bead part 5 Bead core 7 Ablation rubber 8 Carcass 9 Folding part

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Claims (4)

[Claims] The tire bead portion (2) is provided with an abrasion rubber (7) extending radially outward in the tire radial direction, and an end portion of the tire bead around a bead core (5) embedded in the tire bead portion (2) is provided. A carcass (8) having a folded portion (9) wound from the inside toward the outside of the tire
A pneumatic radial tire in which a reinforcing layer (10) is disposed on the outer periphery of the end of the carcass (8) including the turn-back portion (9); H1, the rubber thickness of the abrasion rubber (7) in the vicinity of the winding end of the folded portion (9) is T, the shortest distance from the winding end of the folded portion (9) to the outer surface of the sidewall is L, Assuming that the vertical height from the base of the bead portion (2) to the tire maximum width is H, H1>
A pneumatic radial tire having a range of 0.40H, T <0.04H, and L <0.07H. 2. A carcass (8) including a folded part (9).
Together with the reinforcing layer (10) arranged on the outer periphery of the end of the tire, a reinforcing portion (10A) inside the tire of the reinforcing layer (10) and a portion (8A) inside the tire in the tire bead portion (2) of the carcass (8). The pneumatic radial tire according to claim 1, characterized in that another inner reinforcing layer (11) is interposed between the radial tires. 3. The pneumatic radial tire according to claim 1, wherein a winding height H2 of the reinforcing layer (10) is set lower than a winding height H1 of the folded portion (9). 4. A vertical height position H3 of the another inner reinforcing layer (11) up to a radially outer end is determined by a winding height H1 of the folded portion (9) and a winding height H2 of the reinforcing layer (10).
3. The pneumatic radial tire according to claim 2, wherein the pneumatic tire is set radially outward with respect to.