JP2019111843A - Radial tire for aircraft - Google Patents

Abstract

To provide a tire that can make both improvement in durability of a bead part and weight reduction compatible.SOLUTION: The radial tire for an aircraft comprises a pair of annular cable beads and a radial carcass constituted of at least two plies formed of a plurality of organic fiber cords coated with rubber, toroidally extended between the cable beads. The radial carcass has one or more turn-up plies in which the plies are wound-up outward from inside in a tire width direction of the cable beads and one or more down plies in which the plies are extended at least to inside in a tire radial direction of the cable beads while covering outside in the tire width direction of the wound-up parts of the turn-up plies, whose inner pressure is specified to be in a range of 1000 to 2000kPa. A relation of a ply rating PR in an application size specified in TRA and a diameter A(mm) in a cross-sectional view of a plane including a tire rotary shaft, of the cable bead of the tire satisfies a formula of PR/A≥1.6.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a radial tire for aircraft, and more particularly to a tire that reduces the occurrence of separation of bead portions.

  A radial tire for aircraft (hereinafter also referred to as “tire”) is used under heavy load conditions, and a very high internal pressure is determined by a public standard, and in general, a plurality of plies made of organic fiber cords are reinforced Wood is used for the carcass.

  In such an aircraft radial tire, when heavy load is applied, separation (hereinafter referred to as “rear separation”) sometimes occurs in the bead portion between the ply located at the outermost side in the tire width direction and the rubber. The

  As a means for reducing the above-mentioned back separation, in the radial tire for an aircraft described in Patent Document 1, the separation by the distortion of the rubber can be achieved by optimizing the thickness of the rubber at the back of the bead portion in relation to the rim. We prevent outbreak.

Japanese Patent Application Publication No. 2006-131095

  In recent years, while it is required to reduce fuel consumption of an aircraft from the viewpoint of environmental protection and economy, the demand for weight reduction of tires mounted on the aircraft has also become severe. However, in the method of optimizing the thickness of rubber described in Patent Document 1, there were cases in which the above-mentioned demand for weight reduction could not be sufficiently satisfied. Therefore, there is a need for a tire that can achieve both improvement in durability of the bead portion and weight reduction.

  The inventors of the present invention obtained the following findings as a result of intensive investigation on means for solving the above-mentioned problems. In order to explain the findings, schematic cross-sectional views showing a bead portion of a conventional radial tire for aircraft are shown in FIGS. 1A and 1B. FIG. 1A shows the bead before loading is applied to the tire, and FIG. 1B shows the bead 300 directly under the tire loading, with loading applied to the tire. The cable bead 200 and the radial carcass 400 are embedded in the bead portion 300 of any of the tires shown in FIGS. 1A and 1B. The radial carcass 400 is shown by a single thick line in the figure but is composed of a plurality of laminated plies.

  That is, what is shown in FIG. 1A is the state of the bead portion 300 before the load is applied in a state where the tire is assembled to the rim R and filled with the internal pressure. From this state, when a load is applied to the tire, as shown in FIG. 1B, the bead portion 300 directly under the tire load falls largely to the outer side in the tire width direction (arrow Y1). Then, the ply located at the outermost side of the tire among the plurality of laminated plies is compressed in the longitudinal direction (arrow Y2) of the ply cord. As a result, micro cracks are generated between the organic fiber cords constituting the ply and the rubber in contact therewith. Such micro cracks gradually develop along the cord and eventually become separation between the organic fiber cord and the rubber.

  The inventors further investigated the means for avoiding the occurrence of the cracks based on the above-mentioned knowledge of the process of occurrence of the back separation, and suppressed the occurrence of micro cracks between the organic fiber cord and the rubber. In the present invention, the inventors have found that it is effective to apply a pulling force opposite to the compression in the longitudinal direction of the ply cord, and have completed the present invention.

The gist of the present invention is as follows.
The radial tire for aircraft according to the present invention comprises at least two of a pair of annular cable beads and a ply formed by rubber coating a plurality of organic fiber cords extending in a toroidal shape between the cable beads. And at least one turn-up ply obtained by winding the ply from the inner side in the tire width direction of each cable bead to the outer side, and the ply at the winding portion of the turn-up ply. A radial tire for an aircraft, comprising: at least one downply extended to at least the tire radial direction inner side of the cable bead, covering the tire width direction outer side, and having a specified internal pressure of 1000 to 2000 kPa. Pre-rating PR in the application size defined in Relationship between the diameter A (mm) in the cross section by a plane containing the tire axis of rotation of the soil,
PR / A ≧ 1.6
It is characterized by satisfying.
Here, TRA means TIRE AND RIM ASSOCIATION, INC. Of the United States. Means the standard specified in the latest version of AIRCRAFT YEAR BOOK or EDI (ENGINEERING DESIGN INFORMATION FOR AIRCRAFT TIRES) (the numerical value of the present invention uses the 2017 version) issued by Is an index showing the strength of
In the present invention, “cable bead” refers to a bead core of a cable bead structure.
Further, the prescribed internal pressure in the present invention refers to the application size described in TRA and the air pressure corresponding to the prescribed load of a single wheel in ply rating.

  According to the radial tire for aircraft of the present invention having such a configuration, it is possible to achieve both improvement in durability of the bead portion and weight reduction.

  In the radial tire for aircraft according to the present invention, the relationship between the ply rating PR in the application size defined in the TRA and the diameter A (mm) in a sectional view by a plane including the tire rotation axis of the cable bead of the tire is It is preferable to satisfy 2.11 ≧ PR / A.

  According to the radial tire for aircraft of the present invention having such a configuration, it is possible to prevent excessive shear deformation in the stiffener between the ply and the cable bead, and to avoid the decrease in durability.

  ADVANTAGE OF THE INVENTION By this invention, the tire which can make the durability improvement of a bead part compatible with the weight reduction of a tire can be provided.

It is a schematic sectional drawing which shows the bead part of the conventional radial tire for aircrafts. It is a schematic sectional drawing which shows the bead part of the conventional radial tire for aircrafts. It is a figure which shows the ply structure of the radial tire for aircrafts provided to the experiment. It is a graph which shows an experimental result.

Hereinafter, the experimental result which led to the radial tire for aircraft of this invention is demonstrated.
First, FIG. 2 shows a ply structure of an aircraft radial tire subjected to an experiment. The radial tire 1 for an aircraft shown in FIG. 2 (hereinafter referred to as a tire 1) is rubber-coated with a pair of annular cable beads 2 and a plurality of organic fiber cords extending between the cable beads 2 in a toroidal shape. The radial carcass 4 comprises at least two, seven in the illustrated example, of the radial direction plies, and the radial carcass 4 is one or more of the plies wound from the inner side in the tire width direction of each cable bead. Turnup plies 5a to 5e, and at least one downply 6a and 6b, covering the outer side of the winding portion of the turnup ply 5e in the tire width direction and extending at least to the inner side in the tire radial direction of the cable bead. ,have. Although five turn-up plies 5a to 5e and two down-plies 6a and 6b are shown in FIG. 2, the number is not limited to this, and any number of sheets can be used.

  The behavior of the bead part periphery at the time of filling an internal pressure into a tire is demonstrated using the tire 1 which has said structure.

  When the tire 1 is filled with internal pressure, the rubber in contact with the turnup plies 5a to 5e and the turnup plies 5a to 5e is pulled up toward the tread side along with the diameter growth of the tread of the tire (FIG. 2) Arrow Y3 direction). The cable bead 2 is moved in the rotating direction (the direction of the arrow Y4 in FIG. 2) by the pulling-up operation of the turnup plies 5a to 5e and the surrounding rubber. Furthermore, the pulling up of the turnup plies 5a to 5e and the rotation of the cable bead 2 further pull the down plies 6a and 6b originally pulled by the internal pressure filling together with the surrounding rubber, and move in the Y3 direction. The inventors newly found that when such a pulling force acts on the downply 6b, the compression of the downply 6b at the time of loading described above is relieved.

  Furthermore, as the diameter A (hereinafter, also referred to as a cable bead diameter A) in a cross-sectional view of the cable bead 2 by a plane including the tire rotation axis decreases, the present inventors make the cable bead 2 in the arrow Y4 direction. I also imagined that the rotational movement would be larger. On the other hand, if such rotational movement becomes too large, shear deformation in a stiffener between the ply and the cable bead may be excessive, leading to a decrease in durability.

  Therefore, the inventors conducted various experiments in order to further investigate the requirement for the tensile force acting on the downply 6b to be superior to the compressive force acting on the above-described downply 6b at the time of internal pressure filling. Then, it was newly discovered that the ratio of ply rating and cable bead diameter A is closely related to the above requirements.

That is, the cable bead diameter A is determined in the range which can function as an anchor according to the value of the ply rating of the tire concerned with the design of a tire. However, the inventors focused on the relationship between the ply rating PR and the cable bead diameter A from the viewpoint of the direction of the force acting on the outermost carcass ply, and the durability of the bead portion with respect to tires having various values. Tests to measure the properties were conducted to derive the condition of the ratio PR / A having durability of the bead portion higher than that of the conventional radial tire for aircraft.
Hereinafter, the experimental result in which it came to derive that the ratio between the ply rating PR and the cable bead diameter A is related to the improvement of the durability of the bead portion will be described in detail.

  First, a tire of tire size 1 (52 × 21.0R22 38 PR) and tire size 2 (1400 × 530 R23 42 PR), which are suitable for comparison of tire performance, is manufactured as a evaluation standard and shown in Table 1 The prototype was made based on the specifications, and the cable bead diameter A was changed variously to evaluate the separation durability of the back of the bead portion. The evaluation was performed under the same conditions as in Examples described later, and the obtained evaluation results were organized as a graph, with the vertical axis representing the bead portion durability and the horizontal axis representing the ratio PR / A. The arranged graph is shown in FIG.

As shown in FIG. 3, the bead portion durability is remarkably improved in the tire in which the relationship between the tire ply rating PR and the outer diameter A of the cable bead of the tire satisfies PR / A ≧ 1.6. It can be seen that the separation durability of the back of the bead portion is improved. In the tire which does not satisfy the above-mentioned numerical range, even if it changes ratio PR / A, the improvement effect on bead part endurance is hardly acquired.
Thus, in the radial tire for an aircraft, the inventors of the present invention satisfy the relationship PR / APR1.6 of the tire's ply rating PR and the outer diameter A of the cable bead of the tire. It has been found that the improvement of the durability of the bead portion and the reduction of the weight of the tire can be compatible.

In addition, the relationship between the ply rating PR in the application size defined in TRA and the diameter A of the cable bead of the tire in a sectional view by a plane including the tire rotation axis is 2.111PR / A
It is preferable to satisfy According to this configuration, it is possible to prevent excessive shear deformation in the stiffener between the ply and the cable bead, and to avoid the decrease in durability.

  As a more preferable numerical range, 2.11 ≧ PR / A ≧ 1.65.

  Furthermore, in the radial tire for aircraft according to the present invention, it is preferable to increase the rigidity of the belt or to use a material with the strength of the cable bead increased. For example, the cable bead has a core made of steel formed in an annular shape, and a sheath made of at least one sheath layer in which a sheath filament made of steel is spirally wound around the core. A bead can be used. Furthermore, the carbon content of the sheath filament is preferably 0.90 to 0.95% by mass, and the chromium content is preferably 0.15 to 0.30% by mass. According to such a configuration, even in the case where the outer diameter of the cable bead is smaller than that of the prior art, the anchor function of the bead can be effectively maintained.

Using the tires of tire size 1 and tire size 2 of the specifications shown in Table 1 above, under the specifications shown in Table 2, the separation durability of the back of the bead portion of the tire according to each comparative example and invention example Each was evaluated.
Specifically, the rim assembly in which the tire is assembled to the rim is repeatedly rotated for 10 minutes at a speed of 64 km / h under a predetermined load on the drum, and the number of repetitions in the drum test until rear separation occurs evaluated. The results are shown in Table 2.
The result is that the separation durability of the tire of Comparative Example 1 is 100 for the tire of tire size 1 and the separation durability of the tire of comparative example 3 is 100 for the tire of tire size 2 and the index for each tire size displayed. The larger the index value, the better the separation durability of the back of the bead portion. The weight of the cable bead is 100 (Comparative Example 1) when the cable bead diameter A is 25 mm in the tire size 1 and 100 (Comparative Example 3) when the cable bead diameter A is 27 mm in the tire size 2. The smaller the number, the lighter.

1: Tire 2, 200: Cable bead, 300: Bead portion 4, 400: Radial carcass, 5a, 5b, 5c, 5d, 5e: Turn-up ply, 6a, 6b: Down ply, R: Rim

Claims (2)

A pair of annular cable beads, and a radial carcass consisting of at least two plies of rubber-coated plural organic fiber cords extending in a toroidal shape between the cable beads;
The radial carcass covers one or more turn-up plies in which the plies are wound outward from the inner side in the tire width direction of each cable bead, and covers the outer sides of the turn-up plies in the tire width direction of the turn-up ply. And at least one down ply extended to at least the tire radial direction of the cable bead, and an aircraft radial tire having a prescribed internal pressure of 1000 to 2000 kPa.
The relationship between the ply rating PR in the application size defined in TRA and the diameter A (mm) in a sectional view by a plane including the tire rotation axis of the cable bead of the tire is
PR / A ≧ 1.6
An aircraft radial tire characterized by satisfying. The relationship between the ply rating PR in the application size defined in the TRA and the diameter A (mm) in a sectional view by a plane including the tire rotation axis of the cable bead of the tire is
2.11 PR PR / A
The radial tire for aircraft according to claim 1, wherein

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