JPH06171326A - Radial tire for aircraft - Google Patents

Abstract

PURPOSE:To relax stress concentration directly under the crosssectional center of a bead core by providing the specified relation between the interference to a rim at the cross-sectional center of a bead core and the rim side outer skin thickness of the bead core measured on a straight line passing the cross-sectional center of the bead core and vertical to the rotation axis of a tire. CONSTITUTION:The interference (s) to a tire rim and the rubber gauge (g) at the cross-sectional center of a bead core are set in such a way that the relation between the rubber gauge (g) and the tire rim interference (s) is 1.2-0.6g. Stress concentration directly under the cross sectional center of the bead core 16 is thereby relaxed so as to average contact pressure. During travel, the whole tire bead 24 generates motion in the direction of a rotation axis, and the surface of an outer skin at the lower part of the bead core 16 is rubbed, so that rubber becomes liable to be degraded. It is, therefore necessary to make it hard to transmit fluctuation from a carcass to the part under the bead 24. Accordingly, the interference of the tire rim 22 and the rubber gauge (g) directly under the cross-sectional center of the bead core 16 are set into specified dimension so as to have the relationship of -3.6s +15.7<g to suppress the degradation of rubber.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radial tire for an aircraft, and more particularly, to a radial tire for an aircraft in which a bead core used for fixing the tire to a rim has a circular cross section.

[0002]

2. Description of the Related Art Radial tires for aircraft are often made of organic fiber in a carcass for the purpose of weight reduction. As a bead core for mooring the organic fiber carcass, a circular cross-sectional shape is used for the purpose of avoiding stress concentration at the corners of the bead. Bead cores having

As an example of a radial tire for an aircraft to which a bead core having a circular cross section is applied, Japanese Patent Laid-Open No. 2-2 is known.
As disclosed in No. 00504, there is known a device for solving a relative slip between a rim and a tire when an aircraft performs a sudden braking operation.

In the above example, the slip is solved by optimizing the compression at the time of assembling the rim of the rubber under the bead core (the rim side of the bead core) and by making the shape of the tire base part two-step taper.

[0005]

However, it has been recently revealed by the inventor's investigation that in the above-mentioned tire, the deterioration of the outer skin under the bead core occurs in the middle of a standard tire life.

That is, as shown in FIG. 5 (A), in the tire fitted on the rim 104, the bead core 10 is used.
Since the cross-sectional shape of 0 is circular, 6 as shown in FIG.
Compared to the bead core 102 having a rectangular cross section, the contact pressure immediately below the center of the bead core cross section (the shaded portion in the figure) is very large, and the contact pressure on the toe side is much lower than immediately below the center of the bead core cross section.

Further, since the circular bead core 100 repeats a slight rotation due to a change in the force from the carcass during traveling, the toe 1 is lower than directly below the center of the cross section of the bead core.
There is a problem that the surface of the outer skin where the contact pressure on the 01 side is dropped repeatedly moves inward and outward in the axial direction (direction of arrow W in FIG. 5), which causes rubber to deteriorate and cracks, resulting in long The inventor's research has revealed that it becomes difficult to use the period.

Further, if the tightening margin at the time of rim mounting is reduced to suppress stress concentration, the entire bead portion moves in the tire rotation axis direction during traveling, and this movement rubs the lower portion of the bead core, degrading the rubber. Easier to do.

In view of the above facts, it is an object of the present invention to provide a radial tire for an aircraft, which can suppress deterioration of rubber under a bead core and extend its service life.

[0010]

As a result of various studies by the inventor, a rubber gauge g just below the center of the bead core cross section, a tire
By providing a predetermined relationship with the rim tightening margin s, the stress concentration just below the center of the bead core cross section can be relaxed.
By setting the tightening margin s of the tire / rim and the rubber gauge g at the center of the bead core cross section so that s−0.6 <g, it is possible to effectively alleviate the stress concentration just below the center of the bead core cross section and average the contact pressure. There was found.

Although the stress concentration can be suppressed by reducing the tightening margin s of the tire / rim, the entire tire bead portion moves in the direction of the rotation axis during traveling, and this movement causes the outer skin of the lower portion of the bead core. Since the surface of the rubber is easily rubbed by the rim and the rubber is likely to deteriorate, it is necessary to make it difficult to transmit the fluctuation from the carcass to the bottom of the bead in order to prevent this, and it becomes −3.6s + 15.7 <g. It has been found that the stress concentration immediately below the center of the bead core cross section can be effectively relaxed by setting the tightening margin s of the tire / rim and the rubber gauge g immediately below the center of the bead core cross section to predetermined dimensions.

Further, in the portion from just below the center of the cross section of the bead core to the flange side of the rim, the decrease of the contact pressure is smaller than that on the toe side, and by setting the dimension of this portion within a predetermined range, the total tire and rim are integrated. Adhesion is enhanced,
It was found that relative slip between the rim and the tire can be effectively prevented.

According to a first aspect of the present invention, there is provided a radial tire for an aircraft including a pair of beads having a round cross section, wherein the ply of the radial array cord is used as a toroidal carcass for reinforcing the body, and the plies are anchored in the bead portion. ,
The thickness g of the outer skin on the rim side of the bead core, which is measured on a straight line that passes through the cross-sectional center of the bead core and is perpendicular to the tire rotation axis, and the tightening margin s for the rim at the cross-sectional center of the bead core are 1.2s-0. .6 <g and -3.6s + 1
It is characterized by satisfying 5.7 <g.

According to a second aspect of the present invention, in the radial tire for an aircraft according to the first aspect, a cross-sectional diameter of the bead is e, a straight line passing through a cross-section center of the bead core and parallel to the tire rotation axis is an axial direction of the bead. The distance L between the outer crossing point and the center of the bead core cross section is 1.2 <L /
It is characterized in that the relationship of e <1.5 is satisfied.

[0015]

According to the radial tire for an aircraft of the first aspect of the invention, the outer skin thickness g measured on a straight line passing through the bead cross-section center and perpendicular to the tire rotation axis, and the rim at the bead core cross-section center Tightening margin s is 1.2s-
Since it was set so as to satisfy 0.6 <g and -3.6s + 15.7 <g, the stress concentration just below the center of the bead core cross section is effectively relaxed to average the contact pressure and to the bead of the fluctuation of the carcass. It is possible to prevent the deterioration of the rubber just below the center of the cross section of the bead core by preventing the transmission of

According to the aircraft radial tire of claim 2, in the aircraft radial tire of claim 1, the bead core has a cross-sectional diameter e and a straight bead core passing through the cross-section center of the bead core and parallel to the tire rotation axis. The distance L from the point intersecting the outer skin surface to the center of the bead core cross section is set so as to satisfy the relationship of 1.2 <L / e <1.5. Adhesion is improved and relative slip between the wheel and the tire can be effectively prevented.

The thickness g of the outer skin and the tightening margin s for the rim at the center of the bead core cross section are 1.2s-0.6 <g.
If the range is exceeded, it is not possible to relax the stress concentration just below the center of the bead core cross section, which is not preferable. In addition, if the thickness g of the outer skin is unnecessarily increased,
It is not preferable because the carcass and the rubber may separate on the heel side of the cross section of the bead core.

Further, the thickness g of the outer skin and the tightening margin s for the rim at the center of the bead core cross section are -3.6s + 15.7.
When it exceeds the range of <g, the stress concentration is relieved, but the tire bead part moves in the tire rotation axis direction during traveling, and this movement rubs the outer surface of the bead core lower part with the rim, which easily deteriorates the rubber. Is not preferable.

Further, if the 100% modulus of the rubber in contact with the rim is less than 20 kg / mm ² , the rotation of the bead core around the bead core axis that occurs during running cannot be suppressed and separation occurs between the carcass cord and the rubber. If it exceeds 70 kg / mm ² , stress is likely to be concentrated just below the center of the bead core cross section, which is not preferable.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS.

As shown in FIG. 2, the radial tire for an aircraft of the present embodiment (tire size: H46 × 18.0R2)
The carcass 12 of 0) 10 has 6 layers of toroidal carcass plies 14 in which the carcass ply cords are radially arranged around the tire rotation center, and 4 layers inside the tire of these carcass plies 14 are tire widths. The both ends in the direction are folded back from the inner side in the tire width direction to the outer side around the ring-shaped bead cores 16 arranged at the inner peripheral portion in the tire radial direction, and two layers on the tire outer side are four layers on the tire inner side. Are folded around the bead core 16 from the outer side to the inner side in the tire width direction. The carcass ply 14 of this embodiment is a carcass ply cord made of organic fiber (nylon 6 as an example).
6, 1890d / 3) are substantially parallel to each other and are arranged in the rubber body at an angle of 85 ° to 90 ° with respect to the tire equatorial plane.

Further, the bead core 16 in this embodiment has a structure in which four layers of sheath wire (φ2.3 mm) are spirally wound around an annular core sland (φ5 mm), and is 1 × 5 mm + (10 + 16 + 22 + 28) × 2. Three
The twisted structure is expressed in mm (note that, for example, 10 in parentheses means that 10 sheath wires can be seen in the cross section, but in reality, one sheath wire makes 10 turns. is there.).

The outer side of the carcass 12 in the radial direction of the tire (see FIG. 2).
In the present embodiment, eight belt layers 18 each composed of a belt ply in which organic fibers are embedded in a rubber body are arranged, and a top rubber 20 arranged on the outermost side in the tire radial direction is provided on the upper side of the. It is designed to reinforce.

The aircraft radial tire 10 is fitted to the rim 22. The rim 22 has, for example, a base portion 22B that is inclined 5 ° with respect to the axis and a flange portion 22A that is formed by a plurality of arcs that are smoothly continuous with the base portion 22B.

As shown in FIG. 1, the bead portion 24 of the aircraft radial tire 10 that is fitted into the rim 22 in an interference fit is perpendicular to the tire rotation axis through the center of the cross section of the bead core 16. The relationship between the thickness g of the rubber outer skin 28 measured on the straight line 26 and the interference s for the rim 22 at the center of the bead core cross section is 1.2 s−.
It is set so as to satisfy 0.6 <g and −3.6s + 15.7 <g (note that these relational expressions are not influenced by the tire size). The tightening margin s is calculated by a method of calculating the tightening margin that is usually performed when designing a tire.

Further, in the radial tire for an aircraft of the present embodiment, the cross-sectional diameter e of the bead core 16 and the outer surface of the bead core 16 which is a straight line passing through the center of the cross section of the bead core 16 and parallel to the tire rotation axis intersect the outer surface of the bead core 16. The distance L from the point to the center of the cross section of the bead core 16 is 1.2 <L / e <
It is set to satisfy the relationship of 1.5.

The 100% modulus of the outer skin contacting the rim 22 is preferably 20 kg / mm ² or more and less than 70 kg / mm ² .
More preferably, it is 25 kg / mm ² or more and less than 50 kg / mm ² .

[Test Example] Four types of aircraft radial tires according to the present invention and six types of aircraft radial tires according to Comparative Examples were used in the specifications shown in Table 1 below (prototype tires have 100% modulus of the outer skin in contact with the rim). 50 kg / mm ² and L / e constant, the outer skin thickness g and the tightening margin s for the rim at the center of the bead core cross section are changed.) And these radial tires for aircraft are shown in the table below. Under the test conditions described in No. 1, a drum tester was used in the room to examine the depth of cracks generated in the bead portion, and the results are shown in Table 2 below. In addition, this test is a promotion condition for running under a load 1.2 times the normal use condition.

The fracture index of the bead portion in Table 2 indicates the depth of the crack formed in the bead portion, and is an index display when Comparative Example 5 is set to 100. The smaller the value, the shallower the crack and the damage is. Indicates small.

Further, the relationship between the thickness g of the outer skin and the interference s for the rim 22 at the center of the bead core cross section is 1.2 s-
The range satisfying 0.6 <g and −3.6s + 15.7 <g is shown by the diagonal lines in the graph of FIG. The small circles in the graph indicate each test tire.

[0031]

[Table 1]

[0032]

[Table 2]

Further, three kinds of aircraft radial tires according to the present invention and two kinds of aircraft radial tires according to the comparative example are specified in Table 3 below (thickness of outer skin and tightening to rim at center of bead core cross section). L / e is changed with the value of s being constant, and the modulus of surface rubber at 100% elongation is 50 kg / mm ² ), and these radial tires for aircraft were tested indoors under the following test conditions. The drum tester was used to examine the depth of cracks and the amount of rim displacement that occurred in the base portion, and the results are shown in Table 4. The test is carried out by an indoor drum tester, and the test conditions are as shown in Table 3 below. In addition, the fracture index of the base portion indicates the depth of the crack generated in the base portion as described above.
It is an index display when 00 is set.

[0034]

[Table 3]

[0035]

[Table 4]

Furthermore, two types of aircraft radial tires according to the present invention and four aircraft radial tires according to a comparative example are used.
Seeds (outer skin thickness g is 4.5 mm, tightening margin s for the rim at the center of the bead core cross section is 3.5 mm, L / e value is 1.3
8, the 100% modulus of the outer skin in contact with the rim is changed. ) As a prototype, these radial tires for aircraft were tested with an indoor drum tester under the test conditions shown in Table 1 above, and the depth of cracks and rim displacement that occurred in the bead portion were examined. It was shown to. The fracture index of the bead portion indicates the depth of the crack generated in the bead portion as described above, and is an index display when Comparative Example 4 is 100 in this test.

[0037]

[Table 5]

From the test results of Table 2, Table 4 and Table 5 above, it can be seen that the radial tire for an aircraft to which the present invention is applied is excellent in durability because cracks in the bead portion and rim slippage are small. it is obvious.

[0039]

Since the radial tire for an aircraft according to the first aspect of the present invention has the above-mentioned structure, it has an excellent effect that the deterioration of the outer skin just below the center of the bead core cross section can be prevented and the service life can be extended.

Further, since the radial tire for an aircraft according to a second aspect of the present invention has the above-mentioned structure, the overall adhesion between the tire and the rim is enhanced, and the relative slip between the tire and the rim is effectively prevented. Therefore, it has an excellent effect that the service life can be extended.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a bead portion of a radial tire for an aircraft according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along the axis of a radial tire for an aircraft according to an embodiment of the present invention.

FIG. 3 is a graph showing a relationship between a skin thickness of a radial tire for an aircraft according to an embodiment of the present invention and a tightening margin immediately below a bead core.

FIG. 4 is a cross-sectional view of a bead portion of a radial tire for an aircraft for explaining a separation between a carcass cord and a skin.

5A is a sectional view of a bead portion showing a contact pressure distribution on a rim of a radial tire for an aircraft having a conventional bead core having a circular cross section, and FIG. 5B is a conventional bead core having a hexagonal cross section. FIG. 6 is a cross-sectional view of a bead portion showing a contact pressure distribution with respect to a rim of a radial tire for an aircraft having the above.

[Explanation of symbols]

 10 Radial tires for aircraft 12 Carcass 14 Carcass ply 16 Bead core 22 Rim 24 Bead section

Claims (2)

[Claims] 1. A radial tire for an aircraft, comprising a pair of bead cores having a round cross section, wherein a ply of a radial array cord is used as a toroidal carcass to reinforce the body, and the plies are anchored in a bead portion. The thickness g of the outer skin on the rim side of the bead core measured on a straight line passing through the tire rotation axis and the tightening margin s for the rim at the center of the bead core cross section are 1.2s-0.6 <g and -3.6s + 1
A radial tire for aircraft, which satisfies 5.7 <g. 2. A cross-sectional diameter e of the bead core and a distance L from a point that intersects the outer surface of the bead core in the axially outer side of a straight line passing through the center of the bead core and parallel to the tire rotation axis to the center of the bead core cross section, 1.2 <L / e <1.
The radial tire for an aircraft according to claim 1, wherein the relationship of 5 is satisfied.