Aircraft pneumatic tires

Abstract

The goal is to suppress taxi wear and touchdown wear while ensuring high fracture pressure without significantly increasing weight. [Solution] In the first reference state, the conditions 0 ≤ δ35 / Rc ≤ 0.004 and 0.015 ≤ δ90 / Rc ≤ 0.025 are satisfied, and the belt layers 5a to 5i include two or more spiral belt layers 51 and one or more zigzag belt layers 52, and the two or more spiral belt layers 51 include a first spiral belt layer 511 whose tire width direction edge 51c is located outside the tire width direction of the shoulder circumferential groove 812, and a second spiral belt layer 512 whose tire width direction edge 51c is located between the center circumferential groove 811 and the shoulder circumferential groove 812.

Description

Technical Field

[0004] ,

[0005] , ,

[0001] The present invention relates to a pneumatic tire for an aircraft.

Background Art

[0002] Conventionally, as a pneumatic tire for an aircraft, a belt composed of one or more belt layers arranged on the outer side in the tire radial direction of the crown portion of the carcass is provided. In a predetermined reference state, the radial difference (radius difference) between the outer surface of the tire in the tire equatorial plane and the outer surface of the tire at a tire width direction position spaced apart from the tire equatorial plane by a predetermined distance in the tire width direction is set as a predetermined amount, and a tire having a relatively small radial difference has been proposed (Patent Document 1). According to this tire, while suppressing wear (so-called taxi wear) that occurs when moving within an airport, it is also possible to suppress wear due to slippage under extremely low load when a tire that has stopped at the moment of landing of an aircraft touches the road surface at high speed (so-called touchdown wear).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, as a result of the inventor's intensive study, when the radial difference is relatively small as in the tire described in Patent Document 1 above, and thus the outer surface of the tread portion is made relatively flat in a cross-sectional view in the tire width direction, touchdown wear can be suppressed together with taxi wear. However, the tension applied to the cord of the belt increases, and the burst pressure of the tire (the internal pressure at which the tire breaks when the internal pressure of the tire increases beyond the specified internal pressure) may decrease. It has been found that there is room for improvement in terms of still ensuring a large burst pressure.

[0005] Therefore, the present invention aims to provide an aircraft pneumatic tire that can suppress taxi wear and touchdown wear while ensuring high burst pressure without a significant increase in weight. [Means for solving the problem]

[0006] The means to achieve the above objectives are as follows:

[0007] (1) A first aspect of the present invention is an aircraft pneumatic tire, An aircraft pneumatic tire comprising a pair of bead portions, a carcass consisting of one or more carcass plies toroidally spanning the pair of bead portions, and a belt consisting of three or more belt layers arranged radially outward on the crown portion of the carcass, The outer surface of the tire tread is provided with two center grooves extending in the circumferential direction of the tire, and two shoulder grooves extending in the circumferential direction of the tire and positioned on the outermost side in the tire width direction, outside the center grooves. When the aforementioned aircraft pneumatic tire is mounted on the applicable rim, filled to the specified internal pressure, and then the tire pressure is reduced to 50 kPa, and the tire is unloaded, in the first reference state, let Rc be the tire radius at the outer surface of the tire on the tire equator, let Wb be the distance in the tire width direction from the tire equator to the edge of the widest belt layer where the tire width direction is maximum, let δ35 be the diameter difference between the outer surface of the tire on the tire equator and the outer surface of the tire at a position in the tire width direction 35% outward from the tire equator in the tire width direction by the distance Wb, and let δ90 be the diameter difference between the outer surface of the tire on the tire equator and the outer surface of the tire at a position in the tire width direction 90% outward from the tire equator in the tire width direction by the distance Wb, 0 ≤ δ35 / Rc ≤ 0.004 and 0.015 ≤ δ90 / Rc ≤ 0.025 It satisfies, The aforementioned belt layer is The first belt cord is a ribbon-shaped strip member covered with rubber, which is wound spirally in the circumferential direction of the tire, and consists of two or more spiral belt layers. It includes one or more zigzag belt layers, which are positioned radially outward from the spiral belt layer, and in which a second strip member, which is a ribbon-shaped strip member with a second belt cord covered in rubber, is wound spirally in the circumferential direction of the tire while being folded back at both ends in the width direction of the tire. The two or more spiral belt layers are characterized by comprising: a first spiral belt layer whose edge in the tire width direction is located at a position in the tire width direction that is outside the shoulder circumferential groove; and a second spiral belt layer whose edge in the tire width direction is located at a position in the tire width direction between the center circumferential groove and the shoulder circumferential groove. According to the first aspect of the present invention, a pneumatic tire for aircraft can be used to suppress taxi wear and touchdown wear while ensuring a high burst pressure without a significant increase in weight.

[0008] (2) In the aircraft pneumatic tire described in (1) above (hereinafter also simply referred to as "tire"), It is preferable that the second spiral belt layer is positioned radially outward from the first spiral belt layer. In this case, tire manufacturing becomes easier.

[0009] (3) In the tire of (1) or (2) above, In a cross-sectional view in the tire width direction, when the aforementioned aircraft pneumatic tire is mounted on the applicable rim, filled to the specified internal pressure, and unloaded, the width of the second spiral belt layer in the tire width direction is preferably 25 to 55% of the tread width TW. In this case, it is possible to reduce the weight of the tire while more effectively securing greater destructive pressure.

[0010] (4) In any of the tires described in (1) to (3) above, The number of layers of the first spiral belt layer is preferably 6, and the number of layers of the second spiral belt layer is preferably 1. In this case, a large breaking pressure can be ensured with a minimal increase in weight.

[0011] (5) In any of the tires described in (1) to (4) above, The radial distance between the outer surface of the tire and the zigzag belt layer at the tire equatorial plane is preferably 43 - 52% of the radial distance between the outer surface and the inner surface of the tire at the tire equatorial plane. In this case, sufficient wear performance can be ensured, and the weight of the tire can be reduced.

[0012] (6) In any of the tires described in (1) to (5) above, The groove depths of the two center circumferential grooves and the two shoulder circumferential grooves are preferably 27 - 34% of the radial distance between the outer surface and the inner surface of the tire at the tire equatorial plane. In this case, sufficient drainage performance and durability can be ensured.

[0013] (7) In any of the tires described in (1) to (6) above, When the aircraft pneumatic tire is mounted on the applicable rim, filled with the specified internal pressure, and made unloaded, in the second reference state, in a cross-sectional view in the tire width direction, the rim width RW of the applicable rim and the maximum tire width W satisfy RW / W ≤ 0.7, In the second reference state, in a cross-sectional view in the tire width direction, it is preferable that the tread width TW and the maximum tire width W satisfy 0.73 < TW / W < 0.8. In this case, while ensuring the wear resistance of the tread portion, the durability of the bead portion can be improved.

[0014] (8) In any of the tires described in (1) to (7) above, The number of layers of the zigzag belt layer is preferably 2. In this case, with the minimum number of zigzag belt layers, it is possible to ensure the wear performance, particularly when the aircraft is turning while moving within the airport.

[0015] (9) In any of the tires of (1) to (8) above, a belt protection layer may be provided on the outer side in the tire radial direction of the zigzag belt layer. In this case, the belt can be protected from external injuries and the damage to the belt can be reduced.

[0016] (10) The pneumatic tire for aircraft as the second aspect of the present invention is a pneumatic tire for aircraft including a pair of bead portions, a carcass composed of one or more carcass plies toroidally straddling the pair of bead portions, and a belt composed of three or more belt layers disposed on the outer side in the tire radial direction of the crown portion of the carcass, in a first reference state where the pneumatic tire for aircraft is mounted on an application rim, filled with a specified internal pressure, and then the tire air pressure is reduced to 50 kPa and made unloaded, when the tire radius at the tire outer surface in the tire equatorial plane is Rc, the tire width direction distance from the tire equatorial plane to the edge of the widest belt layer having the maximum tire width direction width is Wb, the radial difference between the tire outer surface in the tire equatorial plane and the tire outer surface at a tire width direction position 35% away from the tire equatorial plane in the tire width direction outside by the distance Wb is δ35, and the radial difference between the tire outer surface in the tire equatorial plane and the tire outer surface at a tire width direction position 90% away from the tire equatorial plane in the tire width direction outside by the distance Wb is δ90, 0 ≦ δ35 / Rc ≦ 0.004 and 0.015 ≦ δ90 / Rc ≦ 0.025 is satisfied, the belt layer is two or more spiral belt layers in a state where a first strip member in a ribbon shape in which a first belt cord is rubber-coated is wound in a helical shape in the tire circumferential direction, It includes one or more zigzag belt layers, which are positioned radially outward from the spiral belt layer, and in which a second strip member, which is a ribbon-shaped strip member with a second belt cord covered in rubber, is wound spirally in the circumferential direction of the tire while being folded back at both ends in the width direction of the tire. The two or more spiral belt layers are characterized by comprising: a first spiral belt layer having a width in the tire width direction greater than 55% of the tread width TW in a cross-sectional view in the tire width direction in a second reference state, where the aircraft pneumatic tire is mounted on the applicable rim, filled to a specified internal pressure, and unloaded; and a second spiral belt layer having a width in the tire width direction of 25 to 55% of the tread width TW in a cross-sectional view in the tire width direction in the second reference state. In a second aspect of the present invention, a pneumatic tire for aircraft can also suppress taxi wear and touchdown wear while ensuring a high burst pressure without a significant increase in weight.

[0017] (11) In the tire of (10) above, It is preferable that the second spiral belt layer is positioned radially outward from the first spiral belt layer. In this case, tire manufacturing becomes easier.

[0018] (12) In the tire of (10) or (11) above, Preferably, the first spiral belt layer has 6 layers, and the second spiral belt layer has 1 layer. In this case, a large inflicting pressure can be secured with minimal weight increase.

[0019] (13) In any of the tires described in (10) to (12) above, The radial distance between the outer surface of the tire and the zigzag belt layer at the tire's equatorial plane is preferably 43-52% of the radial distance between the outer surface of the tire and the inner surface of the tire at the tire's equatorial plane. In this case, it is possible to sufficiently ensure the wear performance and reduce the weight of the tire.

[0020] (14) In any one of the tires of (10) to (13) above, in the tire width direction cross-sectional view in the second reference state, the rim width RW of the applicable rim and the maximum tire width W satisfy RW / W ≤ 0.7. In the tire width direction cross-sectional view in the second reference state, it is preferable that the tread width TW and the maximum tire width W satisfy 0.73 < TW / W < 0.8. In this case, while ensuring the wear resistance of the tread portion, it is possible to improve the durability of the bead portion.

[0021] (15) In any one of the tires of (10) to (14) above, The number of layers of the zigzag belt layer is preferably 2 layers. In this case, with the minimum number of layers of the zigzag belt layer, it is possible to ensure the wear performance particularly when the aircraft turns while moving within the airport.

[0022] (16) In any one of the tires of (10) to (15) above, A belt protection layer may be provided outside the tire radial direction of the zigzag belt layer. In this case, the belt can be protected from external damage and the damage to the belt can be reduced.

Advantages of the Invention

[0023] According to the present invention, it is possible to provide a pneumatic tire for an aircraft that can suppress taxi wear and touchdown wear and can secure a large breaking pressure without a large increase in weight.

Brief Description of the Drawings

[0024] [Figure 1] It is a schematic cross-sectional view in the tire width direction of a pneumatic tire for an aircraft according to an embodiment of the present invention. [Figure 2] It is an enlarged view of the main part of FIG. 1. [Figure 3] This is a diagram illustrating the spiral belt layer. [Figure 4] This is a diagram illustrating the zigzag belt layer. [Modes for carrying out the invention]

[0025] Hereinafter, embodiments of the pneumatic tire for aircraft according to the present invention will be described in detail with reference to the drawings. Common components and parts in each figure are denoted by the same reference numeral. In this specification, "tire circumferential direction" refers to the direction in which the tire rotates around its axis of rotation, "tire radial direction" refers to the direction perpendicular to the tire's axis of rotation, and "tire width direction" refers to the direction parallel to the tire's axis of rotation. Furthermore, in this specification, the side of the tire closer to the axis of rotation along the tire radial direction is referred to as the "inner side in the tire radial direction," and the side of the tire further from the axis of rotation along the tire radial direction is referred to as the "outer side in the tire radial direction." In addition, in this specification, the side of the tire closer to the tire equatorial plane CL along the tire width direction is referred to as the "inner side in the tire width direction," and the side of the tire further from the tire equatorial plane CL along the tire width direction is referred to as the "outer side in the tire width direction." Furthermore, in this specification, "extending in the circumferential direction of the tire" or "wound helically in the circumferential direction of the tire" means extending or wound helically with at least a component in the circumferential direction of the tire, and "extending along the circumferential direction of the tire" means extending parallel to the circumferential direction of the tire (in other words, at an angle of 0° with respect to the circumferential direction of the tire).

[0026] Unless otherwise specified, the positional relationships and dimensions of each element shall be measured under the second reference condition, with the tire mounted on the applicable rim, filled to the specified internal pressure, and unloaded. Furthermore, in this specification, when a tire is mounted on an applicable rim, filled to the specified internal pressure, and subjected to the maximum load, the edges of the contact surface in the tire width direction that come into contact with the road surface are referred to as "tread edges (TE)", and the width in the tire width direction between the two tread edges TE is referred to as "tread width (TW)". Furthermore, in this specification, "circumferential groove" means a groove that extends in the circumferential direction of the tire and has a groove width (opening width to the tread surface) of 2 mm or more.

[0027] In this specification, "Applicable Rim" refers to the standard rim (Design Rim) for the applicable size as described in the latest edition of the AYB (AIRCRAFT YEAR BOOK) or EDI (Engineering Design Information for Aircraft Tires) published by the TRA (The Tire and Rim Association, Inc.) in the United States (numerical values ​​in this specification refer to the 2017 edition), or as to be described in the AYB or EDI in the future. However, for sizes not described in the above standards, "Applicable Rim" refers to the rim applicable to the tire.

[0028] Furthermore, in this specification, "specified internal pressure" refers to the air pressure (maximum air pressure) corresponding to the maximum load capacity of a single wheel in the applicable size and ply rating described in the above standard. However, in the case of a size not described in the above standard, "specified internal pressure" refers to the air pressure (maximum air pressure) corresponding to the maximum load capacity specified for each vehicle on which the tire is mounted. In addition, in this specification, "maximum load" refers to the load corresponding to the maximum load capacity of a single wheel in the applicable size and ply rating described in the above standard. However, in the case of a size not described in the above standard, "maximum load" refers to the load corresponding to the maximum load capacity specified for each vehicle on which the tire is mounted.

[0029] Figure 1 is a schematic cross-sectional view in the tire width direction of an aircraft pneumatic tire according to one embodiment of the present invention. Figure 2 is an enlarged view of the main part of Figure 1. Figure 1 shows a schematic cross-section in the tire width direction in a second reference state, where the tire is mounted on an applicable rim, filled to the specified internal pressure, and unloaded. Figure 2 shows an enlarged view of the main part of Figure 1 in a first reference state, where the tire is mounted on an applicable rim, filled to the specified internal pressure, and then the tire pressure is reduced to 50 kPa and unloaded. In this embodiment, the tire 1 has a symmetrical structure on both sides in the tire width direction with respect to the tire equatorial plane CL as the center (axis of symmetry). Figure 2 is an enlarged view of the main part of one half of the tire 1. However, the tire 1 does not necessarily have to have a symmetrical structure on both sides in the tire width direction with respect to the tire equatorial plane CL.

[0030] As shown in Figure 1, the tire 1 of this embodiment comprises a pair of bead portions 2, a carcass 4 consisting of one or more carcass plies that toroidally straddle the pair of bead portions 2, and a belt 5 consisting of three or more belt layers arranged on the radially outer side of the crown portion of the carcass 4. A tread portion 12 made of tread rubber is arranged on the radially outer side of the belt 5, and a pair of sidewall portions are connected to the tread portion 12.

[0031] A bead core 3 is embedded in the bead portion 2 of the tire 1. In the illustrated example, the bead core 3 consists of an annular cable bead. In the illustrated example, the bead core 3 has a circular cross-section. The bead wire forming the bead core 3 can be made of, for example, high-carbon steel wire. In this example, a bead filler 31 is positioned on the radially outer side of the bead core 3. The bead filler 31 has a roughly triangular cross-section, tapering in width from the inside to the outside in the radial direction of the tire, but the bead filler 31 can have various cross-sectional shapes. For example, one or more known hard rubbers can be used for the bead filler 31.

[0032] The carcass 4 of the tire 1 consists of one or more (for example, 4 to 7, 5 in this embodiment) carcass plies. In this embodiment, the carcass 4 is a radial carcass. More specifically, in this embodiment, the carcass 4 includes one or more (3 in this embodiment) turn-up plies, the ends of which are wound up and fixed around the bead core 3 from the inside to the outside in the tire radial direction, and one or more (2 in this embodiment) down plies, the ends of which cover the ply winding portion of the turn-up plies from the outside in the tire width direction and are fixed without being wound up around the bead core 3. The turn-up plies and down plies are made of, for example, an organic fiber cord such as a nylon cord covered with rubber. However, the carcass 4 may be configured without turn-up plies or down plies.

[0033] As shown in Figures 1 and 2, in this embodiment, the belt 5 consists of three or more belt layers (nine layers in the illustrated example). More specifically, in this example, the belt 5 consists of nine belt layers 5a to 5i, and these belt layers 5a to 5i include two or more (seven layers in the illustrated example) spiral belt layers 51 (belt layers 5a to 5g) and one or more (two layers in the illustrated example) zigzag belt layers 52 (belt layers 5h, 5i) positioned radially outward from the spiral belt layers 51. However, the number of belt layers, and by extension the spiral belt layers 51 and zigzag belt layers 52, is not limited to the above. For example, the number of spiral belt layers 51 can be 2 to 8, and the number of zigzag belt layers can be 2 to 4. From the viewpoint of weight reduction, it is preferable that the total number of belt layers be 10 or less.

[0034] In the illustrated example, in the second reference state, the widths of the belt layers in the tire width direction are, in descending order from largest to smallest, belt layers 5a, 5b, 5c, 5d, 5h=5i, 5e, 5f, and 5g. In the illustrated example, belt layer 5a is the widest belt layer, having the greatest width in the tire width direction. In the first reference state (Figure 2), Wb is defined as the distance in the tire width direction from the tire equatorial plane CL to the edge of the widest belt layer 5a. Note that the widths of the belt layers are not limited to the above example, and any of the belt layers may have the greatest width in the tire width direction, except for the second spiral belt layer 512 (belt layer 5g in the illustrated example), which will be described later.

[0035] Now, let's explain the spiral belt layer. Figure 3 is a diagram illustrating the spiral belt layer. As shown in Figure 3, the spiral belt layer 51 consists of a first belt cord 51b, where a ribbon-shaped first strip member 51a, covered with rubber, is wound spirally in the circumferential direction of the tire.

[0036] As the first belt cord 51b, an organic fiber cord made of an aromatic polyamide such as aramid can be used, or an organic fiber cord made of an aliphatic polyamide such as nylon, or a hybrid fiber cord made of a combination of an aromatic polyamide such as aramid and an aliphatic polyamide such as nylon can be used. As a hybrid fiber cord of aliphatic polyamide fibers and aromatic polyamide fibers, it may be made by twisting together a yarn made of aliphatic polyamide fibers and a yarn made of aromatic polyamide fibers, or it may be made by twisting a yarn that has been pre-compounded with aliphatic polyamide fibers and aromatic polyamide fibers.

[0037] The spiral belt layer 51 is formed by spirally winding a first strip member 51a around the crown portion of the carcass 4 of the green tire in the tire circumferential direction, with each strip member 51a offset by a predetermined amount in the tire width direction so as not to create gaps between adjacent first strip members 51a. The inclination angle of the first belt cord 51b with respect to the tire circumferential direction is, for example, 5° or less. When the spiral belt layer 51 consists of multiple layers, the strip member 51a is folded back when it reaches the tire width edge 51c of the spiral belt layer 51, and begins to be wound onto the outer surface as the next layer, and is wound toward the other tire width edge 51c, thereby creating a stack.

[0038] Next, the zigzag belt layer will be described. Figure 4 is a diagram illustrating the zigzag belt layer. The zigzag belt layer 52 is a state in which a second strip member 52a, which is a ribbon-shaped second belt cord 52b covered with rubber, is wound spirally in the tire circumferential direction, with the second strip member 52a being folded back at both ends 52c in the tire width direction. That is, the second strip member 52a extends from one end 52c in the tire width direction toward the other end 52c, is folded back at the other end 52c, extends from the other end 52c toward the first end 52c, is folded back at the first end 52c, and extends from the first end 52c toward the other end 52c, and this process is repeated. The inclination angle of the second belt cord 52b with respect to the tire circumferential direction is, for example, 5 to 23°.

[0039] As the second belt cord 52b, an organic fiber cord made of an aromatic polyamide such as aramid can be used, or an organic fiber cord made of an aliphatic polyamide such as nylon, or a hybrid fiber cord made of a combination of an aromatic polyamide such as aramid and an aliphatic polyamide such as nylon can be used. As a hybrid fiber cord of aliphatic polyamide fibers and aromatic polyamide fibers, it may be made by twisting together a yarn made of aliphatic polyamide fibers and a yarn made of aromatic polyamide fibers, or it may be made by twisting a yarn that has been pre-compounded with aliphatic polyamide fibers and aromatic polyamide fibers.

[0040] Returning to Figures 1 and 2, in this embodiment, as shown in Figure 2, in the first reference state described above, when the tire 1 has a tire radius of Rc at the tire equatorial plane CL on the tire outer surface 81, and the distance in the tire width direction from the tire equatorial plane CL to the edge of the widest belt layer (belt layer 5a in the illustrated example) which has the maximum width in the tire width direction, and the difference in diameter (difference in radius; the same applies hereinafter) between the tire outer surface 81 at the tire equatorial plane CL and the tire outer surface 81 at a position in the tire width direction that is 35% outward from the tire equatorial plane CL in the tire width direction by a distance Wb, then δ35, and the difference in diameter between the tire outer surface 81 at the tire equatorial plane CL and the tire outer surface 81 at a position in the tire width direction that is 90% outward from the tire equatorial plane CL in the tire width direction by a distance Wb, then δ90, 0 ≤ δ35 / Rc ≤ 0.004 and 0.015 ≤ δ90 / Rc ≤ 0.025 It satisfies the requirements. In addition, if the tread portion 12 has grooves such as circumferential grooves as shown in the illustrated example, the "tire outer surface 81" above shall refer to a hypothetical surface assuming that there are no grooves.

[0041] In this embodiment, as shown in Figures 1 and 2, the tire 1 has a plurality of circumferential grooves extending in the tire circumferential direction on the outer surface 81 (so-called tread surface) of the tread portion 12. More specifically, in this embodiment, the tire 1 has two center circumferential grooves 811 extending in the tire circumferential direction on the outer surface 81 of the tread portion 12, and two shoulder circumferential grooves 812 extending in the tire circumferential direction and positioned on the outermost side in the tire width direction, outside the center circumferential grooves 811. That is, the tire 1 has one center circumferential groove 811 and one shoulder circumferential groove 812 in each half centered on the tire equatorial plane CL. The phrase "positioned on the outermost side in the tire width direction" means that it is positioned on the outermost side in the tire width direction among the plurality of circumferential grooves. That is, in each half centered on the tire equatorial plane CL, the shoulder circumferential grooves 812 are positioned on the outermost side in the tire width direction among the circumferential grooves. In this embodiment, the outer surface 81 of the tread portion 12 of the tire 1 is provided with only the two center circumferential grooves 811 and the two shoulder circumferential grooves 812.

[0042] The above-mentioned circumferential grooves, and by extension the center circumferential groove 811 and shoulder circumferential groove 812, may be zigzag grooves or wave grooves that extend in a zigzag or wave-like manner in the tire circumferential direction at a predetermined inclination angle with respect to the tire circumferential direction, or they may be straight grooves that extend linearly in the tire circumferential direction (i.e., with an inclination angle of 0° with respect to the tire circumferential direction). In this embodiment, both the center circumferential groove 811 and the shoulder circumferential groove 812 are straight grooves.

[0043] In this embodiment, as shown in Figures 1 and 2, the aforementioned two or more spiral belt layers 51 (belt layers 5a to 5g) include a first spiral belt layer 511 (belt layers 5a to 5f in this example) and a second spiral belt layer 512 (belt layer 5g in this example). The edge 51c of the first spiral belt layer 511 is located in the tire width direction, outside the shoulder groove 812. The edge 51c of the second spiral belt layer 512 is located in the tire width direction, between the center groove 811 and the shoulder groove 812 (first aspect of the present invention). Furthermore, the phrase "outside the tire width direction of the shoulder groove 812" means, in a cross-sectional view in the tire width direction in the first and second reference states, outside the opening region of the shoulder groove 812 on the tire outer surface 81, and the phrase "between the center groove 811 and the shoulder groove 812" means, in a cross-sectional view in the tire width direction in the first and second reference states, between the opening region of the center groove 811 on the tire outer surface 81 and the opening region of the shoulder groove 812 on the tire outer surface 81, that is, outside the tire width direction of the opening region of the center groove 811 on the tire outer surface 81, and inside the tire width direction of the opening region of the shoulder groove 812 on the tire outer surface 81, in a cross-sectional view in the tire width direction in the first and second reference states.

[0044] However, in this embodiment, the tire 1 does not have to have only the two center circumferential grooves 811 and the two shoulder circumferential grooves 812 described above on the outer surface 81 of the tread portion 12. For example, the tire 1 does not have to have circumferential grooves on the outer surface 81 of the tread portion 12, and may have circumferential grooves other than the two center circumferential grooves 811 and the two shoulder circumferential grooves 812. Regardless of the presence, number, and arrangement of the circumferential grooves, and the position of the tire width direction edge 51c of the first spiral belt layer 511 and the second spiral belt layer 512 described above, in a cross-sectional view in the tire width direction in the second reference state, the first spiral belt layer 511 (in this example, belt layers 5a to 5f), more specifically all first spiral belt layers 511, may have a tire width direction width W511 greater than 55% of the tread width TW, and the second spiral belt layer 512 (in this example, belt layer 5g), more specifically all second spiral belt layers 512, may have a tire width direction width W512 of 25 to 55% of the tread width TW (second aspect of the present invention). Note that in Figure 1, to avoid complexity, only some of the first spiral belt layers 511 are denoted with the reference numeral "W511".

[0045] Next, the effects and advantages of this embodiment described above will be explained.

[0046] According to the tire 1 of this embodiment, firstly, in the first reference state, δ35 / Rc ≤ 0.004 (δ35 is made relatively small), so that the contact width at the extremely low load at the moment the aircraft lands can be secured, and touchdown wear can be suppressed. Also, in the first reference state, δ90 / Rc ≤ 0.025 (δ90 is made relatively small), so that the drag due to the diameter difference of the tire shoulder when the aircraft moves within the airport can be reduced, and taxi wear can also be suppressed. Furthermore, by setting 0.015 ≤ δ90 / Rc, the belt tension at the shoulder can be increased, and standing wave performance can be improved. Note that since 0 ≤ δ35 / Rc is set, contact centered on the tire equatorial plane CL can be achieved. In summary, according to the tire 1 of this embodiment, taxi wear that occurs when the aircraft moves within the airport can be suppressed, as well as touchdown wear caused by slippage at the extremely low load at the moment the aircraft lands, and standing wave performance can also be improved.

[0047] Furthermore, from the same viewpoint as above, it is more preferable that tire 1 satisfies 0 ≤ δ35 / Rc ≤ 0.002 and 0.018 ≤ δ90 / Rc ≤ 0.023 in the first reference state. Furthermore, the aforementioned distance Wb is preferably 70-90% of the maximum tire width (the maximum width in the tire width direction of tire 1 in the first reference state). This is because setting it to 70% or more can further suppress standing waves, while setting it to 90% or less can reduce weight.

[0048] Furthermore, according to the tire 1 of this embodiment, since the belt layer includes two or more spiral belt layers 51, the wear resistance required for the tread portion 12 can be achieved with fewer belt layers, thereby enabling a lighter tire 1. Furthermore, according to the tire 1 of this embodiment, the belt layer includes one or more zigzag belt layers 52 that are positioned radially outward from the spiral belt layer 51. This suppresses deformation in the width direction of the tire, especially when the aircraft turns while moving within an airport, and improves wear performance during such turns.

[0049] The tire 1 of this embodiment has two center circumferential grooves 811 and two shoulder circumferential grooves 812 on the outer surface 81 of the tread portion 12. This ensures basic drainage performance when an aircraft moves within an airport.

[0050] Here, in the tire 1 of this embodiment, as described above, in the first reference state, 0 ≤ δ35 / Rc ≤ 0.004 and 0.015 ≤ δ90 / Rc ≤ 0.025 are set, so taxi wear and touchdown wear can be suppressed, but on the other hand, it was found that the tire's breaking pressure tends to be small. This is thought to be because, with this configuration, the radius of curvature of the tire outer surface 81 near the tire equatorial plane CL of the tread portion 12 in a cross-sectional view in the tire width direction is relatively large (i.e., the tire outer surface 81 is relatively flat), so the tension applied to the cords of each belt layer is also large. Generally, the tension applied to the cords of a belt layer is proportional to the tire internal pressure and the radius of curvature of the belt layer in a cross-sectional view in the tire width direction. Therefore, in the tire 1 of this embodiment, the two or more spiral belt layers 51 include a first spiral belt layer 511 whose tire widthwise edge 51c is located outside the tire widthwise position of the shoulder circumferential groove 812, and a second spiral belt layer 512 whose tire widthwise edge 51c is located between the center circumferential groove 811 and the shoulder circumferential groove 812 (first aspect of the present invention). Thus, the wide first spiral belt layer 511 ensures the basic wear resistance required for the tread portion 12, and by further providing the narrow second spiral belt layer 512, the strength of the spiral belt layer 51 and the belt layer as a whole can be increased without a significant increase in weight, and consequently, the tire's burst pressure can be greatly increased. Furthermore, in the tire 1 of this embodiment, the edges 51c of both the first spiral belt layer 511 and the second spiral belt layer 512 are not located in the tire width direction position of the circumferential grooves (in this example, the center circumferential groove 811 and the shoulder circumferential groove 812), that is, they are not on the lower side of the circumferential grooves in the tire radial direction. Therefore, deformation of each edge 51c due to pressure from the bottom of each circumferential groove during tire manufacturing is suppressed, and consequently, failures from each edge 51c are also suppressed.

[0051] Based on the above, the tire 1 of this embodiment, more specifically the tire 1 as the first aspect of the present invention, can suppress taxi wear and touchdown wear while ensuring a large burst pressure without a significant increase in weight.

[0052] As described above, in this embodiment, regardless of the presence, number and arrangement of the circumferential grooves, and the position of the tire width direction edge 51c of the first spiral belt layer 511 and the second spiral belt layer 512 described above, in a cross-sectional view in the tire width direction in the second reference state, the first spiral belt layer 511 may have a tire width direction width W511 greater than 55% of the tread width TW, and the second spiral belt layer 512 may have a tire width direction width W512 of 25 to 55% of the tread width TW (second aspect of the present invention). In this case as well, the wide first spiral belt layer 511, that is, the tire width direction width W511 of the first spiral belt layer 511 being greater than 55% of the tread width TW, ensures the basic wear resistance required for the tread portion 12. Furthermore, by providing a narrow second spiral belt layer 512, that is, by providing the tire width direction width W512 of the further provided second spiral belt layer 512 being 25% or more of the tread width TW, the strength of the spiral belt layer 51 and thus the entire belt layer can be increased, thereby ensuring a large fracture pressure. At the same time, because the tire width direction width W512 of the second spiral belt layer 512 is 55% or less of the tread width TW, there is no significant increase in the overall weight of the tire. Based on the above, the tire 1 of this embodiment, or more specifically, the tire as a second embodiment of the present invention, can also suppress taxi wear and touchdown wear while ensuring a large fracture pressure without a significant increase in weight. Furthermore, from the same viewpoint as above, it is more preferable that, in the second reference state, the tire 1 has a width W511 of the first spiral belt layer 511 in the tire width direction that is 65-105% of the tread width TW. Also, it is more preferable that the width W512 of the second spiral belt layer 512 in the tire width direction that is 30-40% of the tread width TW.

[0053] Furthermore, as shown in Figures 1 and 2, and as mentioned above, even when the tire widthwise edge 51c of the first spiral belt layer 511 is located outside the tire widthwise position of the shoulder circumferential groove 812, and the tire widthwise edge 51c of the second spiral belt layer 512 is located between the center circumferential groove 811 and the shoulder circumferential groove 812 (in the case of the first embodiment of the present invention), for the same reasons as above, it is also preferable that, in a cross-sectional view in the tire widthwise direction in the second reference state, the first spiral belt layer 511 has a tire widthwise width W511 greater than 55% of the tread width TW, and the second spiral belt layer 512 has a tire widthwise width W512 of 25-55% of the tread width TW. With this configuration, it is possible to lighten the tire while more effectively securing a large fracture pressure. From a similar viewpoint, even in the above case (the first aspect of the present invention), it is more preferable that, in the second reference state, the tire 1 has a tire width direction width W511 of the first spiral belt layer 511 that is 65 to 105% of the tread width TW. Furthermore, it is more preferable that the tire width direction width W512 of the second spiral belt layer 512 is 30 to 40% of the tread width TW.

[0054] The following describes preferred configurations and other aspects of the tire 1 of this embodiment.

[0055] In this embodiment, as shown in Figures 1 and 2, it is preferable that the second spiral belt layer 512 (belt layer 5g in the illustrated example) is positioned radially outward from the first spiral belt layer 511 (belt layers 5a to 5f in the illustrated example), and more specifically, that the second spiral belt layer 512 is positioned radially outward from all of the first spiral belt layers 511. With this configuration, when manufacturing a tire, if the spiral belt layer 51 is laminated by winding the first strip member 51a from the inside to the outside in the radial direction of the tire, the narrow second spiral belt layer 512 can be laminated on the radially outer side of the wide first spiral belt layer 511, making tire manufacturing easier compared to, for example, the reverse arrangement.

[0056] In this embodiment, as shown in Figures 1 and 2, it is preferable that the first spiral belt layer 511 has 6 layers (belt layers 5a to 5f in the illustrated example) and the second spiral belt layer 512 has 1 layer (belt layer 5g in the illustrated example). With this configuration, for example, compared to the case where the spiral belt layer 51 consists only of the first spiral belt layer 511, a large fracture pressure can be secured with minimal weight increase.

[0057] Referring to Figure 2, in this embodiment, the radial distance T1 between the tire outer surface 81 and the zigzag belt layer 52 (more specifically, the outermost zigzag belt layer in the tire radial direction among the zigzag belt layers 52 (belt layer 5i in the illustrated example)) at the tire equatorial plane CL is preferably 43 to 52% of the radial distance T0 between the tire outer surface 81 and the tire inner surface 82 at the tire equatorial plane CL. This configuration ensures sufficient wear performance while also reducing the weight of the tire. Specifically, if the distance T1 is 43% or more of the distance T0, sufficient wear performance can be ensured, and if it is 52% or less, the weight of the tire can be reduced. Here, the reason why sufficient wear performance can be ensured when the distance T1 is 43% or more of the distance T0 is that, in this embodiment, the spiral belt layer 51 includes a second spiral belt layer 512 in addition to the first spiral belt layer 511, so the rigidity of the tread portion 12 near the tire equatorial plane CL is increased, and even if the distance T1 and thus the thickness of the tread rubber are smaller compared to, for example, the case where the spiral belt layer 51 consists only of the first spiral belt layer 511, sufficient wear performance can be ensured.

[0058] Referring to FIG. 2, in the present embodiment (more specifically, the first aspect of the present invention), the groove depths d of the two center circumferential grooves 811 and the two shoulder circumferential grooves 812 are preferably 27 to 34% of the tire radial distance T0 between the tire outer surface 81 and the tire inner surface 82 on the tire equatorial plane CL. The groove depth d is measured in the depth direction of each circumferential groove. According to this configuration, drainage performance and durability can be sufficiently ensured. That is, since the groove depths d of the two center circumferential grooves 811 and the two shoulder circumferential grooves 812 are both 27% or more of the distance T0, sufficient drainage performance can be ensured, and since they are 34% or less, the volume of the tread rubber can be increased to sufficiently ensure durability. Here, ensuring durability by setting the groove depth d to 34% or less of the distance T0 is particularly effective as a means for sufficiently ensuring durability when the distance T1 and thus the thickness of the tread rubber are small, as described above.

[0059] Referring to FIG. 1, in the present embodiment, in the second reference state, in a cross-sectional view in the tire width direction, the rim width RW of the applicable rim and the tire maximum width W satisfy RW / W ≤ 0.7, and in the second reference state, in a cross-sectional view in the tire width direction, it is preferable that the tread width TW and the tire maximum width W satisfy 0.73 < TW / W < 0.8. The configuration that satisfies "0.73 < TW / W < 0.8" has a relatively narrow tread width TW, and thus is hereinafter also referred to as a "configuration with a narrow tread width". According to this configuration, in the pneumatic aircraft tire 1 with a large load and a very high specified internal pressure, it is possible to improve the durability of the bead portion 2 while ensuring the wear resistance of the tread portion 12. That is, when the tire 1 is a tire with a relatively large maximum tire width satisfying RW / W≤0.7, since 0.73<TW / W, the contact surface with the road surface becomes large, and the wear resistance of the tread portion 12 can be ensured. Also, since TW / W<0.8, it becomes difficult for the bead portion 2 to collapse outward in the tire width direction, and the durability of the bead portion 2 can be improved. Here, since the burst pressure of the tire tends to be smaller for a tire with a smaller tread width TW, applying the specific belt configuration in the above-described embodiment to the tire having the above-described narrow tread width configuration is particularly effective for ensuring a sufficiently large burst pressure of the tire.

[0060] In the present embodiment, as shown in FIGS. 1 and 2, the number of layers of the zigzag belt layer 52 is preferably two layers (in the illustrated example, belt layers 5h and 5i). According to this configuration, it is possible to ensure the wear performance, particularly during turning when the aircraft is moving within the airport, with the minimum number of layers of the zigzag belt layer 52.

[0061] In the present embodiment, as shown in FIGS. 1 and 2, a belt protection layer 6 may be provided outside the zigzag belt layer 52 in the tire radial direction. According to this configuration, the belt protection layer 6 can protect the belt 5 from external damage and reduce the damage to the belt 5. More specifically, when the tire 1 includes the belt protection layer 6, when a protrusion or the like penetrates from the outer surface 81 of the tread portion 12 into the inside of the tire 1, the belt 5 can be protected from damage or the damage to the belt 5 can be reduced. Such a belt protection layer 6 is particularly effective in a pneumatic aircraft tire with a large load and a very high specified internal pressure.

[0062] The belt protection layer 6 can be made of, for example, a highly elastic organic fiber cord such as Kevlar, wound in a wavy or helical pattern in the circumferential direction of the tire. In this embodiment, as shown in Figure 1, the edge of the belt protection layer 6 in the tire width direction is located inward from the tread edge TE in the tire width direction. However, the edge of the belt protection layer 6 in the tire width direction may be located outward from the tread edge TE in the tire width direction. In this embodiment, from the viewpoint of weight reduction, the number of layers of the belt protection layer 6 is one. However, the number of layers of the belt protection layer 6 may be two or more.

[0063] The foregoing describes exemplary embodiments of the present invention, and various modifications can be made without departing from the scope of the claims.

[0064] For example, in the above-described embodiment (more specifically, the second aspect of the present invention), the outer surface 81 of the tread portion 12 of the tire may further be provided with 1 to 3 or 5 or more circumferential grooves extending in the circumferential direction of the tire, and the tire widthwise edge of either the first spiral belt layer 511 or the second spiral belt layer 512 may be located at a tire widthwise position different from the tire widthwise position of any of the circumferential grooves. Even in this case, for example, deformation of each edge during tire manufacturing is suppressed, and consequently, failures originating from each edge are also suppressed. [Industrial applicability]

[0065] The pneumatic tire for aircraft according to the present invention can be suitably used as a pneumatic tire for aircraft of any type and size. Contribution to the United Nations-led Sustainable Development Goals (SDGs)

[0066] The SDGs have been proposed to realize a sustainable society. One embodiment of the present invention is considered to be a technology that can contribute to "No. 12: Responsible Consumption and Production" and "No. 13: Take urgent action to combat climate change and its impacts." [Explanation of Symbols]

[0067] 1: Tire (aircraft pneumatic tire), 12: Tread section, 2: Bead section, 3: Bead core, 31: Bead filler, 4: Carcass, 5: Belt, 5a~5i: Belt layer, 51: Spiral belt layer, 51a: First strip member, 51b: First belt cord, 51c: Edge of spiral belt layer in the tire width direction, 511: First spiral belt layer, 512: Second spiral belt layer, 52: Zigzag belt layer, 52a: Second strip member, 52b: Second belt cord, 52c: End of zigzag belt layer in the tire width direction, 6: Belt protection layer, 81: Outer surface of tire, 811: Center circumferential groove, 812: Shoulder circumferential groove, 82: Inner surface of tire, CL: Tire equatorial plane, d: Groove depth, R: Rim (applicable rim), RW: Rim width, T0, T1: Tire radial distance, TE: Tread edge, TW: Tread width, W: Tire maximum width, W511: Tire width direction width of the first spiral belt layer, W512: Tire width direction width of the second spiral belt layer, Wb: Tire width direction distance

Claims

1. An aircraft pneumatic tire comprising a pair of bead portions, a carcass consisting of one or more carcass plies toroidally spanning the pair of bead portions, and a belt consisting of three or more belt layers arranged radially outward on the crown portion of the carcass, The outer surface of the tread portion of the tire is provided with two center grooves extending in the circumferential direction of the tire, and two shoulder grooves extending in the circumferential direction of the tire and positioned on the outermost side in the tire width direction, outside the center grooves. When the aforementioned aircraft pneumatic tire is mounted on an applicable rim, filled to the specified internal pressure, and then the tire pressure is reduced to 50 kPa, and the tire is unloaded, in a first reference state, let Rc be the tire radius at the outer surface of the tire on the tire equator, let Wb be the distance in the tire width direction from the tire equator to the edge of the widest belt layer where the tire width direction is maximum, let δ35 be the diameter difference between the outer surface of the tire on the tire equator and the outer surface of the tire at a position in the tire width direction 35% outward from the tire equator in the tire width direction by the distance Wb, and let δ90 be the diameter difference between the outer surface of the tire on the tire equator and the outer surface of the tire at a position in the tire width direction 90% outward from the tire equator in the tire width direction by the distance Wb, 0 ≤ δ35 / Rc ≤ 0.004 and 0.015 ≤ δ90 / Rc ≤ 0.025 It satisfies, The aforementioned belt layer is The first belt cord is a ribbon-shaped strip member covered with rubber, which is wound spirally in the circumferential direction of the tire, and consists of two or more spiral belt layers. It includes one or more zigzag belt layers, which are positioned radially outward from the spiral belt layer, and in which a second strip member, which is a ribbon-shaped strip member with a second belt cord covered in rubber, is wound spirally in the circumferential direction of the tire while being folded back at both ends in the width direction of the tire. The two or more spiral belt layers are characterized by comprising: a first spiral belt layer whose edge in the tire width direction is located outside the shoulder circumferential groove in the tire width direction; and a second spiral belt layer whose edge in the tire width direction is located between the center circumferential groove and the shoulder circumferential groove in the tire width direction.

2. The pneumatic tire for an aircraft according to claim 1, wherein the second spiral belt layer is positioned radially outward from the first spiral belt layer.

3. The aircraft pneumatic tire according to claim 1, wherein, in a second reference state, when the aircraft pneumatic tire is mounted on an applicable rim, filled to a specified internal pressure, and unloaded, the width of the second spiral belt layer in the tire width direction in a cross-sectional view in the tire width direction is 25 to 55% of the tread width TW.

4. The pneumatic tire for an aircraft according to claim 1, wherein the first spiral belt layer has six layers and the second spiral belt layer has one layer.

5. The pneumatic tire for aircraft according to claim 1, wherein the radial distance between the outer surface of the tire and the zigzag belt layer at the tire's equatorial plane is 43 to 52% of the radial distance between the outer surface of the tire and the inner surface of the tire at the tire's equatorial plane.

6. The pneumatic tire for aircraft according to claim 1, wherein the groove depth of the two center circumferential grooves and the two shoulder circumferential grooves is 27 to 34% of the radial distance between the outer surface and the inner surface of the tire at the tire's equatorial plane.

7. When the aforementioned aircraft pneumatic tire is mounted on the applicable rim, filled to the specified internal pressure, and unloaded, in a cross-sectional view in the tire width direction, the rim width RW of the applicable rim and the maximum tire width W satisfy RW / W ≤ 0.

7. The pneumatic tire for aircraft according to claim 1, wherein, in the second reference state, in a cross-sectional view in the tire width direction, the tread width TW and the maximum tire width W satisfy 0.73 < TW / W < 0.

8.

8. The number of zigzag belt layers is two, as described in claim 1, for an aircraft pneumatic tire.

9. An aircraft pneumatic tire according to any one of claims 1 to 8, wherein a belt protection layer is provided on the radially outer side of the zigzag belt layer.

10. An aircraft pneumatic tire comprising a pair of bead portions, a carcass consisting of one or more carcass plies toroidally spanning the pair of bead portions, and a belt consisting of three or more belt layers arranged radially outward on the crown portion of the carcass, When the aforementioned aircraft pneumatic tire is mounted on an applicable rim, filled to the specified internal pressure, and then the tire pressure is reduced to 50 kPa, and the tire is unloaded, in a first reference state, let Rc be the tire radius at the outer surface of the tire on the tire equator, let Wb be the distance in the tire width direction from the tire equator to the edge of the widest belt layer where the tire width direction is maximum, let δ35 be the diameter difference between the outer surface of the tire on the tire equator and the outer surface of the tire at a position in the tire width direction 35% outward from the tire equator in the tire width direction by the distance Wb, and let δ90 be the diameter difference between the outer surface of the tire on the tire equator and the outer surface of the tire at a position in the tire width direction 90% outward from the tire equator in the tire width direction by the distance Wb, 0 ≤ δ35 / Rc ≤ 0.004 and 0.015 ≤ δ90 / Rc ≤ 0.025 It satisfies, The aforementioned belt layer is The first belt cord is a ribbon-shaped strip member covered with rubber, which is wound spirally in the circumferential direction of the tire, and consists of two or more spiral belt layers. It includes one or more zigzag belt layers, which are positioned radially outward from the spiral belt layer, and in which a second strip member, which is a ribbon-shaped strip member with a second belt cord covered in rubber, is wound spirally in the circumferential direction of the tire while being folded back at both ends in the width direction of the tire. An aircraft pneumatic tire characterized in that the two or more spiral belt layers include: a first spiral belt layer having a width in the tire width direction greater than 55% of the tread width TW in a cross-sectional view in the tire width direction in a second reference state, when the aircraft pneumatic tire is mounted on an applicable rim, filled to a specified internal pressure, and unloaded; and a second spiral belt layer having a width in the tire width direction of 25 to 55% of the tread width TW in a cross-sectional view in the tire width direction in the second reference state.

11. The pneumatic tire for an aircraft according to claim 10, wherein the second spiral belt layer is positioned radially outward from the first spiral belt layer.

12. The pneumatic tire for an aircraft according to claim 10, wherein the first spiral belt layer has six layers and the second spiral belt layer has one layer.

13. The pneumatic tire for aircraft according to claim 10, wherein the radial distance between the outer surface of the tire and the zigzag belt layer at the tire's equatorial plane is 43 to 52% of the radial distance between the outer surface of the tire and the inner surface of the tire at the tire's equatorial plane.

14. In the second reference state, in a cross-sectional view in the tire width direction, the rim width RW of the applicable rim and the maximum tire width W satisfy RW / W ≤ 0.

7. The pneumatic tire for aircraft according to claim 10, wherein, in the second reference state, in a cross-sectional view in the tire width direction, the tread width TW and the maximum tire width W satisfy 0.73 < TW / W < 0.

8.

15. The number of zigzag belt layers is two, as described in claim 10, for an aircraft pneumatic tire.

16. An aircraft pneumatic tire according to any one of claims 10 to 15, wherein a belt protection layer is provided on the radially outer side of the zigzag belt layer.

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