JPH01160712A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE:To improve the durability of a bead, in a tire for an aircraft, by providing a reinforcement layer consisting of a reinforcing member of a prescribed Poisson's ratio on the tire-axis directional outside of the carcass being wound around a bead core. CONSTITUTION:The inside carcass ply 15A of a carcass 15 is wound around on a bead core 12 from the inside to the outside, and the outside carcass ply 15B from the outside to the inside respectively. And a reinforcement layer 20 of semicircular section is arranged in the circumferential direction between the outside carcass ply 15B and a side wall 16, and in the neighborhood where the side wall 16 is in contact with a rim flange 18a. The reinforcement layer 20 is made up of a reinforcement member having Poisson's ratio of 0.48 or below By this constitution, separation trouble of the bead at the time when high-speed running is repeated under a high-load condition can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to improving the bead durability of a pneumatic radial tire, for example, a pneumatic radial tire for aircraft running at high speed under heavy loads.

(Prior art) As a conventional pneumatic radial tire, for example,
There is something like the one shown in the figure. In Figure 5, l is a pneumatic radial tire, and pneumatic radial tire l
has a pair of beads 3 having a bead core 2 in the center, and a carcass 5 which extends between the beads 3 in a toroidal shape and is wound around the bead core 2. The carcass 5 has an inner carcass ply 5A wound around the bead core 2 from the inside to the outside, and an outer carcass ply 5I wound around the bead core 2 from the outside to the inside, and has a so-called bead up-down structure. be. In addition to this, the bead structure of pneumatic radial tires includes:
There is also a so-called bead high turn-up structure in which the bead core 2 of only the inner carcass ply 5A is wound from the inside to the outside and upward. 6 is a side wall, and the bead 3 is assembled to the rim 8.

When such a pneumatic radial tire 1 is mounted on an aircraft and takes off and lands, the pneumatic radial tire 1 repeatedly travels at high speed under a heavy load. In particular, during landing, the pneumatic radial tire 1 receives a high load of 200% of the normal load, and as shown by the two-dot chain line in FIG. Repeat bending until contact is made. Finally, there is a problem in that a peeling failure 9 occurs between the lower part 6a of the sidewall 6 and the carcass.

Until now, there has been no technology to suppress these bead separation failures.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a pneumatic radial tire that can significantly suppress the occurrence of bead separation failure even when the tire is repeatedly driven at high speeds under high loads such as M landings of aircraft.

(Means for Solving the Problems) The present inventors have conducted various studies on the causes of peeling failures that occur in the beads of tires running at high speeds under high loads, and on structures for preventing peeling failures. Ta. As a result, bead failure occurs on the outer surface of the outer carcass ply 58 in the bead up-down configuration;
In the bead high turn-up structure, the inner carcass ply 5 is wound from the inside of the bead core 2 to the outside.
, occurs on the outer surface of. Separation failure occurs due to the main shear stress τ occurring at the interface between the carcass cord, which is difficult to stretch, and the sidewall rubber, which is easy to stretch. Due to this principal shear stress τ. It has been found that reducing this is effective in suppressing peeling failures.

Principal shear stress τ. As shown in FIG. 1, if the outer surface path from the outer surface of the bead in contact with the rim flange of the bead to the outermost layer of the carcass is 1iIIth13 (represented by h), then the following formula τ is obtained. It is indicated by the ooh-heavy/fu relationship. Further, in detail, it is shown by the following formula 〇a. Here, R, G, and a are the rim flange radius of curvature, rim flange contact width, and rubber shear rigidity, respectively, and are constants. Therefore, if the outer surface path lh is simply increased, the main shear stress τ will increase as shown in FIG. is reduced.

However, the volume and weight of the bead increases, and the amount of heat generated by the bead during negative rolling increases, resulting in even worse results. In particular, in pneumatic radial tires used under heavy loads and high speeds, such as pneumatic radial tires for aircraft, the internal temperature of the bead reaches a high temperature that directly leads to failure, so the outer surface distance increases. cannot be increased.

Also, the principal shear stress τ. is related to the Poisson's ratio ν of the member adjacent to the cord of the carcass ply, such as the rubber or polymeric material of the sidewall, and the principal shear stress τ. is τ. It is in the relationship of Sen ν5.3. More specifically, the relationship is expressed by the following formula.

Here, RSG, a is a constant as described above. Therefore,
By making Poisson's ratio ν smaller than 0.5, the principal shear stress τ. As shown in FIG. 4, it has been found that this can be significantly reduced.

The present inventors further conducted various studies and arrived at the present invention.

That is, the pneumatic radial tire according to the present invention includes a pair of beads having a bead core in the center, and cords that span between the beads in a toroidal manner, are wound around the bead core from the inside to the outside, and are arranged parallel to each other in the radial direction. A pneumatic radial tire comprising: a carcass having a carcass wound around the bead core; and a reinforcing layer made of a reinforcing member having a Poisson's ratio of 0.48 or less is provided on the outside in the tire axial direction of the carcass wrapped around the bead core. .

Here, the Poisson's ratio ν of the reinforcing member is set to be 0.48 or less because if it exceeds 0.48, the main shear stress τ will be reduced. The reason for this is that the reduction in bead durability is as small as 25% or less compared to the conventional case, and the effects of the present invention cannot be sufficiently obtained and bead durability performance cannot be improved.

(Function) When a pneumatic radial tire runs at high speed under heavy load,
The tire flexes significantly and the bead comes into contact with the rim flange, and a large reaction force from the rim flange acts repeatedly on the bead. This reaction force generates a large main shear stress on the outer side of the carcass in the axial direction of the tire. However, since the pneumatic radial tire of the present invention has a reinforcing layer with a Poisson's ratio of 0.48 or less on the outer side of the bead carcass in the tire axial direction, the generation of main shear stress is significantly suppressed, and 25 % is reduced. Therefore, even if repeated stress is applied to the outside of the carcass, the main shearing stress is significantly alleviated by the reinforcing layer, the repeated stress on the outside of the carcass is significantly reduced, and the occurrence of peeling failure is suppressed. The durability of the bead is greatly increased.

(Example) Embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows Example 1 of a pneumatic radial tire according to the present invention.

First, the configuration will be explained. In FIG. 1, 11 is a pneumatic radial tire, and the pneumatic radial tire 11 is an aircraft tire with a tire size of H4G-18R20. The pneumatic radial tire 11 has a pair of beads 13 having a bead core 12 in the center, and a carcass 15 that extends between the beads 13 in a toroidal manner and is wound around the bead core 12. carcass 15
The three inner carcass plies 15A are wound around the bead core 12 from the inside of the pneumatic radial tire 11 to the vicinity 15A of the tire maximum width position P, and the bead core 12 is wound from the outside of the tire to the inside up to 15 mb near the bead toe 13a. Two outer carcass plies 15. It is an amplifier-down structure having. Each inner carcass ply 15A is rubber coated 1890 d/
Consisting of 3 denier nylon cord, each outer carcass ply 15° is rubber coated 1890 d/3
Made of denier nylon cord. Reference numeral 16 denotes sidewall rubber, which is provided to cover the outer side of the carcass 15 in the axial direction up to the bead heel 13b. 1
8 is a rim, and the pneumatic radial tire 11 is assembled to the rim 18 by beads 13. 20 is an external stiffener (indicated by diagonal lines in the figure) as a reinforcing layer, and the external stiffener 20 is attached to the outer carcass ply 1.
5. and side wall 16.
is provided in the circumferential direction near the rim flange 18a of the rim 18 in contact with the rim flange 18a and has a semicircular cross section. External stiffener 20
The thickness D2° is approximately 1 of the thickness h13 from the surface of the outer carcass ply 1511 to the outer surface of the sidewall 1G.
/2. Poisson's ratio of external stiffener 20 is 0.3
0, and the modulus at 100% extension is 42.3 kg.
f/cal. The external stiffener 20 is made of foamed rubber having a large number of fine cells, and the foaming rate of the foamed rubber is V.
s is 200. The foaming rate Vs is calculated using the following formula: Foaming rate Vs = (Volume of bubbles) / (Volume of rubber) x 10
0.

The foamed rubber may be foam-like urethane or an elastic member.
8a and receives a large reaction force from the rim flange 18a, the external stiffener 20 alleviates this reaction force,
Large principal shear stress τ. significantly suppress the occurrence of Reference numeral 21 denotes an internal stiffener 21 adjacent to the upper side of the bead core 12 and located inside the carcass 15. On the outside of the crown part of the carcass 15 (not shown) is a nylon cord 6.
Two belt braais are provided in the circumferential direction. The configuration other than the above is the same as a normal pneumatic radial tire for aircraft.

Next, Examples 2 to 4 according to the present invention will be described.

In Examples 2 to 4, the Poisson's ratio ν of the external stiffener 20 in Example 1 was 0.30, whereas the Poisson's ratio ν was 0.40, 0.45, 0.48, and 1.
The modulus at 00% elongation and the foaming rate Vs of the foamed rubber forming the external stiffener 20 are shown in the following table. The other configurations are the same as in the first embodiment.

(This page, hereafter in the margin) Next, Example 5 of the present invention will be described. FIG. 2 shows Example 5 of a pneumatic radial tire according to the present invention.

In the pneumatic radial tire 31 of Example 5, the bead has an up-down structure in Example 1, whereas it has a turn-up structure. This is a case in which the external stiffener 20 is provided between the inner carcass ply 15A and the sidewall 1G on the outer side of the inner carcass ply 15A wound up from the inside to the outside of the bead core 12. The characteristics of the external stiffener 20 are the same as those of the first embodiment. The inner carcass ply 15 is made of Kevlar cord. Other configurations and operations are the same as in Example 1.

Next, Examples 6 to 8 according to the present invention will be described. In Examples 6 to 8, the Poisson's ratio ν of the external stiffener 20 was 0.30 in Example 5, whereas the Poisson's ratio ν was 0.40, 0.45, 0.48, and 100%.
The modulus at time and the foaming rate Vs of the foamed rubber are shown in the diagram. The other configurations are the same as in the fifth embodiment.

Next, 10 types of test tires (8 types of Examples and 2 types of Comparative Examples) were prepared, and the effects of the present invention were confirmed.

The test tires were as shown in the diagram, Examples 1 to 4 and Examples 5 to 8 were those shown in Figures 1 and 2, respectively, and the characteristics of the external stiffener 20 were changed as shown in the diagram. It is something. Everything other than the above is the same. Also, Comparative Example 1.2
are the same as those in FIG. 5 and FIG. 2 described above, except for the external stiffener 20, and other than the external stiffener 20, they are the same as in the 1.5th embodiment.

The test was conducted using an indoor drum testing machine to test the durability of the beads. The test tire was filled with an internal pressure of 14.1 kg/d, loaded with a load of 24 OLons, and tested according to the American standard TS.
The test was carried out on O-C62 under 120% TAXi conditions and expressed as the number of times until failure occurred. The number of times may be 35 or more, and preferably 45 or more. The results of the bead durability test are shown in the diagram.

As shown in the chart, the test results show that Examples 1 to 4 and Examples 5 to 8 were each significantly superior to Comparative Example 1.2.

(Effects) As explained above, according to the present invention, by providing a reinforcing layer on the bead, occurrence of bead peeling failure is significantly suppressed during repeated high-speed travel under high loads such as during takeoff and landing of an aircraft. can.

[Brief explanation of the drawing]

FIG. 1.2 is a partial sectional view showing a 1.5th embodiment of the pneumatic radial tire according to the present invention. Figure 3 shows the principal shear stress τ. FIG. 4 is a graph showing the relationship between the distance and the outer surface distance, and FIG. 4 shows the principal shear stress τ. It is a graph showing the relationship between and Poisson's ratio ν. FIG. 5 is a partial sectional view showing a conventional pneumatic radial tire. 11.31...Pneumatic radial tire, 12
...Bead core, 13...Bead, 15...Carcass, 15A...Inner carcass ply, 15,...
...Outer carcass sprue I, 20...External stiffener (tlli stratum), h...Outer surface distance, τ. ...Principal shear stress, ν...Poisson's ratio.

Claims (2)

[Claims] (1) A carcass comprising: a pair of beads having a bead core in the center; and a carcass having cords that span between the beads in a toroidal manner, are wrapped around the bead core from the inside to the outside, and are arranged parallel to each other in the radial direction. 1. A pneumatic radial tire, characterized in that a reinforcing layer made of a reinforcing member having a Poisson's ratio of 0.48 or less is provided on the axially outer side of the carcass wound around the bead core. (2) The pneumatic radial tire according to claim 1, wherein the reinforcing member is foamed rubber.