JPS6237204A - Tire for aircraft - Google Patents

Abstract

PURPOSE:To improve shock absorbing effect when taking off or landing while to protect the opposite ends of belt layer from damage by specifying the elastic modulus of carcass cord, belt layer band cord and reinforcing layer cord while constructing the bead apex into double radial layers. CONSTITUTION:It is constructed with carcass 2-4 having the cord angle against the tire equator of 60 deg.-90 deg., a belt layer 5 having the cord angle of 0 deg.-30 deg. and a band 8 having the cord angle against the circumferential direction of tire lower than 5 deg.. The cords of carcass 2-4 and the belt layer 5 are composed of organic fiber cord having tensile elastic modulus lower than 5,000kg/mm<2>. The bead apex 7 is constructed into double layer of hard rubber having the dynamic elastic modulus higher than 500kgf/cm<2> and soft rubber having the dynamic elastic modulus in the range of 100-500kgf/cm<2>. With such arrangement, shock absorbing effect when taking off and landing can be improved while the opposite ends of belt layer can be protected from damage.

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention has sufficient load capacity, can withstand the centrifugal force associated with high-speed rotation during takeoff and landing of an aircraft, and can effectively alleviate the impact of the aircraft. Regarding aircraft tires.

(Prior Art) Aircraft have made remarkable progress in recent years, and as aircraft weight and flight speed have increased, the characteristics of safely taking off and landing at high speeds as well as withstanding high loads and high speeds have become more demanding. In particular, the following characteristics are required for aircraft tires that differ from general tires.

b) Aircraft tires must be able to reduce the impact when an aircraft lands on a runway, stop the aircraft safely, and facilitate take-off; therefore, the structure of the tire should be designed from the above perspective.

It is necessary to select tire reinforcing materials.

Aircraft tires are designed to have a large amount of deflection under load, for example, approximately 28% to 38%, in order to effectively cushion the impact of the aircraft and ensure safe takeoff and landing. Therefore, it is necessary to select a tire structure and reinforcing material that can sufficiently withstand large repeated deformations.

c) Since the weight and size of aircraft tires are limited in order to reduce the weight of the aircraft as much as possible, the load on each tire is extremely large.

For example, in the case of general tires, the load per unit weight in the standard state is about 50 times, whereas in the case of aircraft tires, it is 130 to 360 times. Also, regarding the internal pressure used, general tires are at most about 8 kg/CA, while aircraft tires are at about 10 to 1 kg/CA.
This is an extremely high pressure of 6 kg/-. Therefore, the reinforcing material of the tire must have sufficient strength to withstand this.

As mentioned above, it is necessary for aircraft tires to satisfy all of the required characteristics, but conventionally, this type of tire has often used a cross-ply structure in which the carcass cords are configured to cross each other between the plies. . Due to the direction in which the carcass cords are arranged, tires with this type of structure have low rigidity in the tread portion, which is unfavorable in terms of wear resistance and heat generation. Furthermore, the center of the tread protrudes due to the centrifugal force accompanying high-speed rotation of the tire, causing temporary and permanent tire growth, which is unsatisfactory in terms of tire durability.

Therefore, we adopted a so-called radial structure in which carcass cords are arranged in the tire's radial direction, and by placing a belt layer on the inside of the tread in which highly elastic cords are arranged at a relatively shallow angle in the circumferential direction of the tire, we increase the rigidity of the tread. Recently, radial tires have come into use. This type of radial tire has a problem in that its carcass cords are arranged in the radial direction, and the high elasticity cords in the belt layer are arranged at a shallow angle in the tire circumferential direction, resulting in poor impact mitigation effects during takeoff and landing. There is a problem of damage occurring due to large amounts of strain at both ends of the belt layer.

(Problems to be Solved) This invention solves the problems of wear resistance, heat generation, and tire growth in a cross-ply structure, and is based on a radial structure, including carcass cords, belt layer cords, and reinforcing layers. The purpose of the present invention is to provide an aircraft tire in which the elastic modulus of the cord is set within a specific range and the bead apex has a two-layer structure, thereby increasing the effect of mitigating shock during takeoff and landing of an aircraft while preventing damage to both ends of the belt layer. shall be.

(Technical Means for Solving the Problems) In this invention, both ends are folded back and locked around a pair of left and right bead cores, and the cord is fixed at an angle of 60° to the tire equatorial plane.
A carcass arranged at an angle of ~90° and a cord placed outside the carcass at an angle of ~30° with respect to the tire equatorial plane.
A belt layer arranged at a cord angle of 100°, and a bead apex arranged in an area surrounded by the sagging band, carcass, and its folded part arranged above the belt layer at a cord angle of 5 inches or less in the circumferential direction of the tire. A reinforcing layer is provided outside the bead apex and extends from the bead bottom to the sidewall part, and the cords of the carcass and the belt layer are both organic fiber cords with a tensile modulus of 5000 kg/mm" or less, and the bead Apex is an aircraft tire characterized by being composed of two layers: hard rubber placed on the inside of the tire and soft rubber placed adjacent to the hard rubber on the outside of the tire.

The present invention will be described in detail below with reference to the drawings.

FIG. 1 shows the right half of a sectional view of the tire of the present invention, and FIGS. 2(a) to 2(d) show schematic views of the belt layer and the band. In the figure, the tire T is secured by two carcass plies 2.3, which are secured by folding back the ends from the inside to the outside around the bead core 1, and by folding back the ends from the outside to the inside around the bead core 1. The carcass has a carcass made of one carcass ply 4, and a belt layer 5 and band 8 made of organic fiber cords on the outside of the crown part of the carcass. The cords of the carcass are arranged at an angle of 600 to 90" to the tire equatorial plane, but in order to particularly increase the lateral rigidity of the tire, the cords of the carcass are arranged at an angle of 79 to 80" to intersect with each other. It is preferable to do so. Next, the tensile modulus of the carcass and belt layer cords is 500.
0 kg'/mm2 or less, preferably 1000 kg/
It is composed of organic fiber cords with a diameter of less than 1.5 mm.As mentioned above, aircraft tires have a large amount of deflection when loaded.
Moreover, it is subjected to repeated bending deformation due to high-speed rotation.

Therefore, aircraft tires not only have sufficient bending fatigue resistance under large deformations, but also prevent ply separation between the carcass and the belt layer due to the difference in stiffness near the boundary between the carcass and the belt layer at both ends. That is important.

Therefore, the present invention provides a relatively low elastic modulus for both the carcass ply cord and the belt layer cord, particularly 5000 k
By using an organic fiber cord with a weight of less than 1.5 g/mm, the bending durability is increased, and the elastic modulus of the carcass cord and the belt layer cord are made close to each other, thereby effectively suppressing stress concentration at the end of the belt layer. This made it possible.

Table 1 shows the basic physical properties of organic fiber and inorganic fiber cords commonly used as carcass cords and belt layer cords.

In addition to those listed in Table 1, the organic fiber cords that can be used in the present invention include polyvinyl alcohol fibers and polyvinylidene chloride fibers.

Polyvinyl chloride fiber, polyacrylonitrile fiber,
Fibers such as polyethylene fibers, polyurethane fibers, cellulose fibers, and cellulose ester fibers can be used, especially those with a tensile modulus of 1000 kg/mm among the above.
2 or less, a fiber cord such as nylon 66 is preferred. The cords of the carcass and the cords of the belt layer are made of substantially the same material, for example, by using nylon 66 for both the carcass cord and the cord of the belt layer, the carcass effectively absorbs the repeated impact received from the tread part of the belt layer. This will help prevent damage to the tread.

Next, in the present invention, the carcass 2.3 and its folded part 2a,
15% to 50% of the tire cross-sectional height H in the area surrounded by 3a
The bead apex 7 extends to a height Hf of %.

The bead apex 7 consists of a triangular hard rubber 7a extending from the upper side of the bead core toward the sidewall on the inside of the tire, and a soft rubber 7b adjacent to the hard rubber 7a and arranged on the outside of the tire. This heat apex 7
The upper end 2a of the folded part of the carcass is further strengthened by the arrangement of the hard rubber 7b, and the fit with the wheel is further strengthened.
, 3a is absorbed and alleviated. In addition, the upper part of the bead is made of relatively flexible soft rubber, so it deforms repeatedly during driving.

It effectively reduces impact and further improves the durability of the bead.

Therefore, hard rubber has a relatively low position, for example, Hs/ll.
It is preferable that the one-sided soft rubber 7b, whose value of X100 is kept in the range of 15 to 35%, extends above the hard rubber 7a and is arranged below so as to cover at least the folded portion of the carcass. The dynamic elastic modulus (E) of the hard rubber 7a is 500 kgf/an! As mentioned above, the dynamic elastic modulus (E) of the soft rubber 7b is 100 to 50
It is in the range of 0 kgf/cnl.

Here, the dynamic elastic modulus (E) of the bead apex was measured using a viscoelasticity spectrometer manufactured by Himoto Seisakusho at a temperature of 77°C, an initial strain of 10%, an amplitude of 2.0%, and a frequency of 59 Hz.
This is a value measured using a sample of crane width x 3011 length x 2 mm thickness.

Next, in the present invention, a reinforcing layer 9,10 extending from the bottom of the bead in the direction of the sidewall is provided on the outside of the bead ape nox. The reinforcing layer preferably requires at least two plies, the cords of which are at an angle of 30° to the radial direction of the tire.
They are arranged to intersect each other at an angle of ~60°. And its upper end height +1. ) lc is preferably in the range of 20% to 70%, preferably 30% to 65%, of the tire cross-sectional height H, and is preferably arranged so as not to overlap the folded upper end of the carcass ply and the upper end position of the bead apex.

Note that the cord of the reinforcing layer is the same as that of the carcass or has a high elastic modulus.

In addition, in the present invention, since a cord with a relatively low elastic modulus is used for the cord of the belt layer, the "tag effect" of the belt layer tends to decrease. The effect can be maintained.

Next, the cords of the belt layer are arranged at an angle of 30° or less, preferably 20° or less with respect to the tire circumferential direction. Conventionally, in general tires, the cord of the belt layer was set in the range of 15° to 45° to adjust for the "tag effect" and the "envelope effect" of the tread. There is a phenomenon in which the tire crown protrudes due to the centrifugal force that accompanies rotation, and there is a problem with tire growth.
If this phenomenon continues for a long period of time, the tire will be permanently set in a growing state, causing increased heat generation and reduced durability.

Therefore, in the present invention, it is preferable to arrange a band made of cords having an elastic modulus equal to or higher than the cords of the belt layer on the outside of the belt layer, thereby increasing the tire's hoop effect and sufficiently withstanding the centrifugal force accompanying high-speed rotation of the tire. Tire growth can be effectively suppressed.

The width Wa of this band is 20% to 70% of the width Wb of the belt layer.
% range is necessary to improve durability, but even when used in combination with a band exceeding 90%, the effect of tire growth can be expected. It is preferable that the cords of the band are arranged Oo in the circumferential direction of the tire, but they can also be arranged at an angle of 5 degrees or less, and when using multiple plies, the cords should be arranged so that they intersect with each other. You can also do it.

FIGS. 2(a) to 2(d) show schematic diagrams of the arrangement of the belt layer and the band. Figure 2 (a) shows a state in which a band made up of two plies C1 and C2 is placed above a belt layer B made up of two folded plies B1 and B2;
Figure (B) shows a case where the first ply C1 of the band uses a ply divided around the tire equator.
Using a band made of two plies, Figure 2 (D)
1 shows a belt layer in which both ends are folded back and a second ply B2 which is not folded back is placed inside the first ply B1, and the folded ply is used as a band.

In addition, in the present invention, stress concentration at both ends of the heald layer is effectively absorbed by arranging cushion rubber 6 whose thickness gradually decreases from both ends of the heald layer between the heald layer and the carcass below both ends of the heald layer. , can be relaxed. Cushion rubber 6 has a 300% modulus of 70 to 150 kg.
/cnt range is used.

Further, in the present invention, the modulus of the topping rubber of the carcass and belt layer is a relatively soft rubber corresponding to the elastic modulus of the cord, for example, a 300% modulus of 80 to 160.
kg/cnl, preferably 90-110 kg/cflI
range is used.

EXAMPLE Aircraft tires with a tire size of 26 x 6.6 had the basic structure shown in FIG. 1, and tires with various specifications shown in Table 2 were manufactured as prototypes, and the durability of each tire was evaluated. The durability test indicates the number of take-offs and taxi simulations leading to failure according to the TSO-C62c test defined by the National Civil Aviation Administration standard.

In Table 2 showing the evaluation results, the examples in which the reinforcing layer was set to a predetermined height and the belt layer cord was made of nylon 66 or polyester, while the band was made of steel, aramid, or rayon, all met the durability test standard. It is recognized that the test passes.

(Effects of the Invention) As described above, the aircraft tire of the present invention uses a specific organic fiber cord having a relatively low modulus of elasticity for both the carcass cord and the cord of the belt layer, and also arranges a band on the upper side of the heddle layer. In addition, a two-layer bead apex and reinforcing layer are placed in the bead, which prevents lifting caused by centrifugal force during high-speed rotation during takeoff and landing, effectively cushioning the aircraft, and also prevents repeated tire deformation. By absorbing and relaxing strain, an aircraft tire with excellent durability can be obtained.

[Brief explanation of the drawing]

Figure 1 shows the right half of the cross-sectional view of the tire of the present invention, and Figures 2 (A), 2 (B), and 3 (A) to 3 (E) show cross-sectional views of the belt layer. . T...Tire, 1...Bead core, 2.3.4...Carcass ply 5...Belt layer 6...Cushion rubber 7...Bead apex 7a...Hard rubber 7b...・Soft rubber 8...Band. 9.10... Reinforcement layer. Patent Applicant Sumitomo Rubber Industries Co., Ltd. Agent Patent Attorney Yoshihira Nakamura Figure 1 Figure 2 (a) Figure 2 ((1) Figure 2 (8) Procedural Amendment Statement September 3, 1985 Patent Office Director Kuro 1) Mr. Akihiro 1, Indication of the case: Patent Application No. 65490 of 1985 2, Title of invention: Aircraft tire 3, Person making the amendment: August 6, 1988 - August 26, 1988) 6. Correct the 7 lines subject to correction as follows.

Claims (4)

[Claims] (1) Both ends are folded back and locked around a pair of left and right bead cores, and the cord is 60° to 90° to the tire equatorial plane.
A carcass arranged at an angle of 0°, a belt layer arranged outside the carcass and having cords arranged at an angle of 0° to 30° with respect to the tire equatorial plane, and a belt layer arranged at an angle of 0° to 30° with respect to the tire equatorial plane; comprising a bead apex arranged in an area surrounded by the band and the carcass and its folded part arranged at a cord angle of 5 degrees or less, and a reinforcing layer extending from the bead bottom to the sidewall part outside the bead apex, The cords of the carcass and the belt layer are both organic fiber cords with a tensile modulus of 5,000 kg/mm^2 or less, and the bead apex includes a hard rubber placed inside the tire and a cord adjacent to the hard rubber outside the tire. An aircraft tire characterized by being comprised of two layers of soft rubber disposed on. (2) The tensile modulus of the carcass cord is 1000 kg/
The aircraft tire according to claim 1, which has a diameter of mm^2 or less. (3) The aircraft tire according to claim 1, wherein the belt layer is constituted by a folded ply. (4) Dynamic elastic modulus (E) of hard rubber is 500 kgf/c
m^2 or more, and the dynamic elastic modulus (E) of soft rubber is 10
The aircraft tire according to claim 1, which has a particle diameter in the range of 0 to 500 kgf/cm^2.