JP2006062544A - Radial tire containing air for aircraft - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radial tire containing air for aircraft which is lightweight, prevents generation of a breakdown of a bead part due to a separation or the like at the junction of rubber members, and improves the durability of the bead part. <P>SOLUTION: A rubber chafer and a second stiffener of the radial tire containing air for the aircraft are arranged between a point a and a point b. The rubber chafer has a coefficient of elasticity α of 3.1 to 4.6 MPa at the time of 100% elongation, and the second stiffener has a coefficient of elasticity β of 2.5 to 3.7 MPa at the time of 100% elongation. Then a linear dimension between the point a and the point c is expressed by the following formula, 0.24×(α/P) to 0.35×(α/P), and a linear dimension between the point b and the point c is expressed by the following formula, 1.69×(β/P) to 2.03×(β/P). Then an elasticity coefficient γ of side rubber at the time of 100% elongation is 1.2 to 2.1 MPa, and a creeping distance between the point a and a point d on the tire surface is 15.6 to 64.2 % of the distance between a contact point A, which is a linear dimension on a rim flange, and a most outward point E of the rim flange. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an aircraft pneumatic radial tire (hereinafter also simply referred to as “tire”), and more particularly to an aircraft pneumatic radial tire with improved bead durability.

  Since pneumatic radial tires for aircraft are used under severe conditions such as high loads and high speeds, the burden on the bead portion in the rim contact area is large. In particular, the use conditions of tires (ply Considering that (rating) becomes severe, further improvement in bead durability is required. The maximum ply rating of an aircraft pneumatic tire is currently 40PR for the main tire and 36PR for the nose tire.

In general, as a method for improving the durability of the bead portion, a method of reducing the reaction force from the rim by increasing the thickness of a reinforcing rubber layer such as a rubber chafer or a second stiffener provided in the bead portion. It has been known. Various studies have also been made on techniques for improving the bead portion durability by prescribing the physical properties and arrangement locations of the respective reinforcing rubbers (for example, described in Patent Documents 1 to 7).
JP 2001-30722 A (Claims etc.) JP 2002-36829 A (Claims etc.) JP 2002-293113 A (Claims etc.) JP-A-2-11405 (claims, etc.) Japanese Patent Laid-Open No. 3-16812 (Claims etc.) Japanese Patent Laid-Open No. 5-92709 (claims, etc.) JP-A-7-144516 (Claims etc.)

  However, since weight reduction is required for aircraft tires, it is necessary not only to increase the thickness of the reinforcing rubber layer in the entire bead portion, but to increase the gauge only at the necessary portions. Also, if the joint between the side rubber and rubber chafer is placed within the contact area with the rim, separation of the joint may occur, so the position of the joint is removed from the contact area with the rim to prevent separation. It is also necessary as a design considering the bead portion durability. As described above, various techniques for improving the durability of the bead portion by improving the bead portion structure have been studied and proposed, and more excellent bead portion durability can be achieved while satisfying these requirements. There is a need to provide a pneumatic radial tire for aircraft.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a pneumatic radial tire for an aircraft in which bead portion durability is improved by reducing the weight and preventing occurrence of a bead portion failure due to separation or the like at a joint portion of a rubber member. There is.

In order to solve the above-described problems, the pneumatic radial tire for aircraft according to the present invention is folded and locked from the tire inner side to the outer side around a pair of bead portions and a bead core embedded in each of the pair of bead portions. A carcass having a rubber-coated radial arrangement cord of two or more plies, a tread portion positioned on the outer periphery of the crown portion of the carcass, and a pair of sidewall portions positioned on the side portions of the carcass, wherein the bead portion includes the carcass A rubber chafer disposed on the outer periphery of the folded portion; a first stiffener extending from the bead core between the carcass; and a second stiffener disposed between the rubber chafer and the folded carcass. In pneumatic radial tires for aircraft,
The point a is the point where the outer surface of the bead part is in contact with the contact point A between the straight part and the curved part of the rim flange when it is assembled to the regular rim specified in TRA and filled with normal internal pressure and 150% of the normal load is applied. When the intersection point intersecting the outermost layer ply surface of the carcass in which the perpendicular line dropped in the carcass direction with respect to the tire surface under the conditions of 0 bar internal pressure and no load from the point a is defined as a point b, Between the point b, the rubber chafer having an elastic modulus α at a 100% elongation of 3.1 to 4.6 MPa and the second elastic modulus β at a 100% elongation of 2.5 to 3.7 MPa. Stiffener and are placed,
The contact pressure generated at the point a by the rim reaction force when the point a comes into contact with the contact A when the normal load is 150% of the normal load is set to P (kPa). And when the intersecting point where the perpendicular intersects the outer surface of the second stiffener is point c, the linear distance between point a and point c is
0.24 × (α / P) to 0.35 × (α / P)
And the linear distance between point b and point c is
1.69 × (β / P) to 2.03 × (β / P)
Represented by
The elastic modulus γ at the time of 100% extension of the side rubber of the sidewall adjacent to the rubber chafer is 1.2 to 2.1 MPa, and a joint portion on the tire surface between the side rubber and the rubber chafer is defined as a point d. 15.6 to 64.2% of the distance between the contact A and the outermost point E of the rim flange where the creepage distance between the points a and d on the tire surface is a linear distance on the rim flange. It is characterized by being.

  Here, the pneumatic tire of the present invention is used by being attached to a standard rim defined in a standard issued by TRA (USA) according to each size, and this standard rim is usually called a regular rim. . Thus, “regular rim” refers to a standard rim in the applicable size specified in the 2002 YEAR BOOK issued by the United States Tire and Rim Association TRA. Similarly, "regular load" and "regular internal pressure" refer to the maximum load and the air pressure for the maximum load in the applicable size and ply rating defined in the 2002 YEAR BOOK issued by the United States Tire and Rim Association TRA. .

  According to the present invention, it is possible to provide a pneumatic radial tire for an aircraft in which the occurrence of a bead portion failure due to separation or the like at a joint portion of a rubber member is prevented while reducing the weight, and the bead portion durability is improved. Can do. Thereby, durability of the bead part of the tire for aircraft which has become severer by the enlargement of an airplane can be secured.

Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 and 2.
FIG. 1 is a left side sectional view of an essential part of an assembly of a bead portion and a rim of an aircraft pneumatic radial tire according to the present invention. FIG. 2 is a cross-sectional view showing the upper half of FIG. 1 further enlarged.

  This tire has a pair of bead portions (only one of them is shown) and a rubber-coated radial array cord of two or more plies that are folded and locked around the bead cores 1 embedded in the pair of bead portions from the inside to the outside. Carcass 2, a tread portion (not shown) located on the outer periphery of the crown portion of the carcass 2, and a pair of sidewall portions 6 located on the side portions of the carcass 2.

  The bead portion includes a rubber chafer 3 disposed on the outer periphery of the carcass folding portion, a first stiffener 4 extending from the bead core 1 between the carcass 2a and the folded carcass 2b, and the rubber chafer 3 being folded back. And a second stiffener 5 arranged between the carcass 2b.

  In the present invention, in the tire having the above structure, it is assembled with the regular rim 7 defined in the TRA, filled with the regular internal pressure, and the outer surface of the bead portion is the straight portion and the curved portion of the rim flange when loaded with 150% of the regular load. The point a that contacts the contact point A is defined as a point a, and the outermost ply surface of the carcass 2b in which a perpendicular L that is lowered in the carcass direction with respect to the tire surface under the condition of 0 bar internal pressure and no load from the point a is folded When the intersecting intersection is a point b, between the point a and the point b, the rubber chafer 3 having an elastic modulus α at the time of 100% elongation of 3.1 to 4.6 MPa and the elastic modulus at the time of 100% elongation. First, it is important that the second stiffener 5 having β of 2.5 to 3.7 MPa is disposed.

  The 100% elastic modulus α, β of each of the rubber chafer 3 and the second stiffener 5 is likely to break due to brittle fatigue if it exceeds the above upper limit value. The ability to relax the reaction force will be reduced. The “0 bar internal pressure, no load” means a state in which the normal internal pressure is filled, the load is canceled and the internal pressure is released from the 150% normal load state.

In addition, the contact pressure generated at the point a by the rim reaction force when the point a comes into contact with the contact A when 150% of the normal load is loaded is assembled into the normal rim 7 defined in the TRA, and P (kPa) ), And an intersection where the perpendicular L intersects the outer surface of the second stiffener 5 is a point c, the linear distance between the points a and c is expressed by the following equation:
0.24 × (α / P) to 0.35 × (α / P)
And the linear distance between point b and point c is
1.69 × (β / P) to 2.03 × (β / P)
It is also important to be expressed as

  The straight line distance (ac) between the points a and c in the rubber chafer 3 and the straight line distance (b through c) between the points b and c in the second stiffener 5 are each 0.24 ×. When the value is less than the value of (α / P) and 1.69 × (β / P), the strain due to the contact pressure generated at the point Aa due to the rim reaction force cannot be relaxed, and the point b is the starting point. Will occur. Conversely, when the straight line distance (ac) and the straight line (bc) exceed the values of 0.35 × (α / P) and 2.03 × (β / P), respectively, heat accumulation As the amount increases, the physical properties of the rubber change, resulting in a bead failure.

  Further, the elastic modulus γ at 100% elongation of the side rubber 6 on the side wall adjacent to the rubber chafer 3 is 1.2 to 2.1 MPa, and the joint between the side rubber 6 and the rubber chafer 3 on the tire surface is pointed out. When d, the creepage distance (ad) between the point a and the point d on the tire surface is a linear distance on the rim flange 15 of the distance between the contact A and the outermost point E of the rim flange. It is also important that it is from 6 to 64.2%. This point E is an intersection of lines indicating the flange width and the flange height defined in TRA.

  If the 100% elastic modulus γ of the side rubber 6 exceeds 2.1 MPa, it tends to break due to brittle fatigue, while if it falls below 1.2 MPa, the ability to relieve the reaction force from the rim 7 decreases. Further, at the point d where the rubber chafer 3 and the side rubber 6 are joined, in order to avoid the separation of the joined part, it is necessary to be away from the contact area with the rim 7, and the creeping distance on the tire surface ( a to d) need to be 15.6% or more of the linear distances A to E on the rim flange. Further, since the side rubber 6 is used which has better ozone degradation resistance than the rubber chafer 3, the d point may be close to the rim in order to reduce ozone degradation of the bead portion in contact with the outside air. preferable. Therefore, the point d needs to have the rim line as the upper limit position, and the creepage distance (ad) needs to be 64.2% or less of the linear distances A to E on the rim flange.

Hereinafter, the present invention will be described specifically by way of examples.
Under the conditions shown in Table 1 below, test tires of Examples and Conventional Examples were produced.

Each of the obtained test tires was subjected to a durability test using a drum testing machine shown below. The results are shown in Table 2 below.
<contents of the test>
Each test tire is filled with normal internal pressure, and the following tests (1) to (4) are passed if the test is completed without any trouble.
(1) 50 takeoff tests at 100% normal load (2) 8 taxi tests at 100% normal load (3) 2 taxi tests at 120% normal load (4) 150% normal load Takeoff test once

  As shown in Table 2 above, the test tires of the examples completed the tests (1) to (4), and there was no abnormality in the nondestructive inspection after the test. On the other hand, in the test tire of the conventional example, the swelling from the inside of the tire occurred at the point a on the tire surface in the test (4) and was cracked.

It is a principal part left sectional view of the assembly of the bead part and rim of the pneumatic radial tire for airplanes concerning one embodiment of the present invention. It is sectional drawing which expands and shows the upper half of FIG.

Explanation of symbols

1 Bead Core 2 Carcass 3 Rubber Chafer 4 First Stiffener 5 Second Stiffener 6 Side Wall (Side Rubber)
7 rims

Claims (1)

A pair of bead portions, a carcass of a rubber-coated radial arrangement cord of two or more plies, which is folded and locked around the bead core embedded in each of the pair of bead portions from the inside of the tire, and an outer periphery of the crown portion of the carcass A tread portion located on the side of the carcass, and a pair of sidewall portions located on the side portion of the carcass, and a bead core, a rubber chafer disposed on an outer periphery of the carcass folding portion, and a bead core between the carcass In a pneumatic radial tire for an aircraft, comprising: a first stiffener extending in a tapered manner; and a second stiffener disposed between the rubber chafer and the folded carcass.
The point a is the point where the outer surface of the bead part is in contact with the contact point A between the straight part and the curved part of the rim flange when it is assembled to the regular rim specified in TRA and filled with normal internal pressure and 150% of the normal load is applied. When the intersection point intersecting the outermost layer ply surface of the carcass in which the perpendicular line dropped in the carcass direction with respect to the tire surface under the conditions of 0 bar internal pressure and no load from the point a is defined as a point b, Between the point b, the rubber chafer having an elastic modulus α at a 100% elongation of 3.1 to 4.6 MPa and the second elastic modulus β at a 100% elongation of 2.5 to 3.7 MPa. Stiffener and are placed,
The contact pressure generated at the point a by the rim reaction force when the point a comes into contact with the contact A when the normal load is 150% of the normal load is set to P (kPa). And when the intersecting point where the perpendicular intersects the outer surface of the second stiffener is point c, the linear distance between point a and point c is
0.24 × (α / P) to 0.35 × (α / P)
And the linear distance between point b and point c is
1.69 × (β / P) to 2.03 × (β / P)
Represented by
The elastic modulus γ at the time of 100% extension of the side rubber of the sidewall adjacent to the rubber chafer is 1.2 to 2.1 MPa, and a joint portion on the tire surface between the side rubber and the rubber chafer is a point d. 15.6 to 64.2% of the distance between the contact A and the outermost point E of the rim flange where the creepage distance between the points a and d on the tire surface is a linear distance on the rim flange. A pneumatic radial tire for an aircraft characterized by being.

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