JPH01215606A - Aircraft pneumatic radial tire - Google Patents

Abstract

PURPOSE:To improve the durability of a bead area by locating the junction of a turnup ply and a down ply in a carcass on the side of bead core rather than the normal of a rim flange section profile curve in a specific range. CONSTITUTION:A carcass 1 consists of one turnup ply 4 which is folded from the inside to the outside of a tire around a bead core 2, and one down ply 6 which extends toward a bead toe along the outside of a folded area 5. In this case, the junction A of the both plies 4, 6 which makes an angle of 45 deg. to the rotation axis l of the tire, is located near the side of a bead core 2 rather than normal (a boundary line) m of the section profile curve of a rim flange 3 in the range where it contacts the outer wall of a bead area when a load is applied to the tire. And the junction A is placed within the range between the boundary line m and a tangent n which is parallel to the rotation axis l of the bead core 2.

Description

Detailed Description of the Invention (Industrial Field of Application) This invention relates to pneumatic radial tires for aircraft used under heavy loads and high speeds, and in particular improves the durability of the bead by reducing the amount of heat generated at the bead. We will describe the technology that improves this.

(Prior art) Aircraft radial tires must have both high-speed resistance and heavy-load resistance, so the carcass is made of a large number of plies, and the bead section is made by layering the plies of the carcass around the bead core from the inside of the tire to the outside. It has a so-called up-down structure that combines a turn-up ply that has been wound back and a down ply that extends toward the bead toe along the outside of the folded part.Furthermore, a base made of hard rubber is placed on the bead core, and it is integrated with this base. A stiffener is embedded in the bead rubber.

Therefore, the bead area tends to become enlarged, and as this type of tire is used under heavy loads and high speeds, the bead area rapidly generates heat and its temperature rises, causing separation, etc. Decreases the durability of the bead.

Therefore, attempts have been made to make the rubber material of the bead part lower in heat generation, but this is still not sufficient.

(Problems to be Solved by the Invention) The present invention aims to reduce the amount of heat generated in the bead by improving the structure of the bead, thereby improving the durability of the bead.

(Means for Solving the Problems) This invention provides a winding method in which plies made of organic fiber cords arranged parallel to each other in a direction substantially orthogonal to the equatorial plane of the tire are wound around a bead core from the inside of the tire to the outside. A pneumatic radial tire with a toroidal carcass consisting of a nap ply and a down ply extending along the outside of the folded part toward the bead toe, when mounted on a regular rim and filled with the regular internal pressure. In the radial cross section, the rim flange cross-sectional contour curve in the area where the turnup ply and its folded part or the confluence with the down ply make an angle of 45° with the axis of rotation of the tire and contact with the outer wall of the beat part under load. This pneumatic radial tire for aircraft is characterized by being located closer to the bead core than the normal line.

Now, FIG. 1 illustrates the structure of a bead portion of a pneumatic radial tire for aircraft according to the present invention.

In the figure, 1 is a carcass, 2 is a bead core, and 3 is a rim flange.

In this example, the carcass 1 includes one turn-up ply 4 wrapped around a bead core 2 from the inside of the tire to the outside, and one down ply 6 extending along the outside of the turned-up part 5 toward the bead toe. It becomes an up-down stack consisting of.

The confluence point A of the turnup ply 4 and down ply 6 forms an angle of 45° with the rotational axis l of the tire (shown as a line parallel to the rotational axis in the drawing), and when a load is applied to the tire, the bead It is arranged closer to the bead core 2 than the normal line (hereinafter referred to as a boundary line) m of the cross-sectional contour curve of the rim flange 3 in the region that contacts the outer wall. Note that it is impossible to locate the confluence point A on the rim base side beyond the bead core 2, so the confluence point A is placed in the area sandwiched between the boundary line m and the tangent line n parallel to the rotation axis l of the bead core 20. It is.

Further, FIGS. 2(a) to 2(C) show other bead portion structures according to the present invention.

Figure (a) shows the turn-up ply 4 and its reversing part 5.
An example in which the confluence point A with the
) is an example where the confluence point A is placed on the boundary line m, and the same figure (
C) shows an example in which the turn-up ply 4 is made of two layers, and the junction A of the turn-up ply 4 and the folded portion 5a located on the outside thereof is arranged in the above-mentioned region.

(Function) In a tire with a carcass that is laminated up and down by wrapping the heply from the inside of the tire to the outside around a bead core, the stiffness of the region of the bead, that is, the height of the stiffener, is extremely high due to the heat generation of the bead. There is a close relationship. In particular, in tires with large bead deformations such as radial tires for aircraft, there is a significant difference in durability depending on the setting of the region with large rigidity. This phenomenon will be explained according to FIG.

The illustrated example tire has a structure in which the height of the stiffener 7 is high, that is, the confluence point A of the turnup ply 4 and the down ply 6 is located closer to the tire outer wall surface than the boundary line m, and deformation is extremely high during load transfer. Stiffener up to the growing area α,
In other words, a region with high rigidity extends, and the carcass is forced to deform due to shear deformation.
Shear strain is concentrated in the separation generation area β on the down ply 6 and the top portion T of the stiffener.

On the other hand, if the current flow point A is placed in a region on the bead core side from the boundary line m, the rigidity in the region where the deformation is large is reduced, so that bending deformation of the bead portion becomes possible. Then, the compressive strain in the radial direction increases in the separation generation area on the down ply, thereby suppressing a reduction in shear strain, particularly the concentration of shear strain at the top of the stiffener, and improving the durability of the bead portion.

(Example) Size H46X18. For OR20, radial structure using ply made of nylon cord (1890d/3) Nylon cord (1890d/3) is attached to the crown part of the carcass.
/3) An aircraft tire in which the tread part is reinforced by arranging a belt consisting of six layers arranged substantially parallel to the tire circumferential direction, and the bead part is as shown in Fig. 1 and Fig. 2 (a) and (C). Each tire was manufactured with the structure shown in Figures 4 (a) to (C), and the FAA (Federal Aviation Administration) T
Durability is determined by how many cycles it can run based on the 120% load and taxiing conditions specified in SO-C62.
I did B. The results are shown in the table below. The size of the rim that incorporates the tire is rim flange height 1.5 inches, rim width 11.0 inches, and rim flange radius of curvature 0.9 inches.
5 in., and the test was conducted at an internal pressure of 14.1 kg/cnf,
The test was carried out with a load of 24 tOn.

(Effects of the Invention) This invention improves the durability of the bead part of a pneumatic radial tire used for an aircraft wheel, which is required under load, especially under severe conditions such as long taxiing runs. Realized.

[Brief explanation of the drawing]

FIGS. 1 and 2 (a) to (C) are cross-sectional views showing the bead structure according to the present invention, and FIGS. 3 and 4 (a) to (C) are cross-sectional views of the conventional bead part. . 1... Carcass 2... Bead core 3.
...Rim flange 4...Turnup ply 5
...Folded part 6...Down ply 7...
・Staifuna A...Confluence point m...Boundary line
n...Tangent l...Rotation axis

Claims (1)

[Claims] 1. A turn-up ply in which plies made of organic fiber cords arranged in parallel to each other in a direction substantially orthogonal to the equatorial plane of the tire are wound around a bead core from the inside of the tire to the outside, and the folded back. A pneumatic radial tire with a toroidal carcass consisting of a down ply extending along the outside of the bead toe and extending toward the bead toe. The confluence of the ply and its folded portion or down ply is located closer to the bead core than the normal to the rim flange cross-sectional profile curve in the area that makes contact with the outer wall of the bead portion during load, which forms an angle of 45° with the rotational axis of the tire. A pneumatic radial tire for aircraft.