JP5060784B2 - Aircraft pneumatic tire - Google Patents

Description

  The present invention relates to an aircraft pneumatic tire, and more particularly to an aircraft pneumatic tire that reduces the tire weight and greatly improves durability during heavy load running.

  Aircraft pneumatic tires are installed on heavy-duty aircraft and run on the runway under harsh conditions of use, including passengers, cargo and fuel when taking off, and while fuel is low when landing, along with deceleration of the aircraft Since the load applied to the tire increases, it is required to have excellent durability when traveling under heavy loads. On the other hand, pneumatic tires for aircraft are used during take-off and landing, but are completely unnecessary in the air, so there is a strong demand for a reduction in tire weight.

  In addition, since the pneumatic tire for aircraft is subjected to a large load, the deflection of the tire in use is set to be extremely large. And the deformation of the cord constituting the carcass is also increased. In addition, a large compressive force acts on the cord due to local bending deformation, and at the time of tire load rolling, the compressive force repeatedly acts on the cord, so that there is a problem that the cord is easily fractured. . In particular, when the cord is an organic fiber cord, fatigue fracture tends to occur significantly.

  In order to solve this problem, a method using an organic fiber cord of relatively high strength as a cord constituting the carcass is generally used. Further increase in strength of the organic fiber cord, selection of an arrangement position thereof, and the cord The placement of the interlayer rubber between the carcass plies to be formed and the design of the shape have been carried out to improve the durability during heavy load running.

  For example, in Japanese Patent Laid-Open No. 6-1105 (Patent Document 1), as an aircraft pneumatic tire capable of improving the strength of the carcass while reducing the weight of the tire, the organic fiber cord constituting the carcass has a strength of 9.0 g / d. An aircraft pneumatic tire to which the above high-strength nylon cord is applied is disclosed.

  On the other hand, in JP-A-6-143913 (Patent Document 2), a carcass or the like is configured as a pneumatic bias tire that is excellent in fracture pressure resistance, burst resistance, and cut burst resistance and can reduce tire weight. A pneumatic bias tire is disclosed in which an ultrahigh strength polyamide fiber cord oriented at a specific inclination angle and having a strength of 9.0 gr / d or more is applied to an organic fiber cord.

JP-A-6-1105 JP-A-6-143913

  However, as a result of studies by the present inventors, when a tire generates heat due to running under heavy load, an organic fiber cord such as a high-strength nylon cord used in a conventional aircraft pneumatic tire has a limit temperature for maintaining strength. It has been found that there is still room for improvement in terms of improving the durability of the tire when running under heavy loads.

  Accordingly, an object of the present invention is to provide a pneumatic tire for an aircraft that solves the above-described problems of the prior art, can reduce the tire weight, and can greatly improve the durability during heavy load running. is there.

  As a result of diligent investigations to achieve the above object, the present inventors have identified a cord constituting the down ply in an aircraft pneumatic tire having a biased carcass composed of a turn-up ply and a down ply. By applying an organic fiber cord having a thermal shrinkage stress and an elastic modulus, the weight of an aircraft pneumatic tire can be reduced and the durability during heavy load running can be greatly improved, and the present invention is completed. It came to.

That is, the aircraft pneumatic tire of the present invention has a pair of bead portions and a pair of sidewall portions, and a tread portion connected to both sidewall portions, and at least two pairs embedded in the pair of bead portions. A bead core and a carcass having a bias structure composed of a plurality of carcass plies each extending in a toroidal shape between the pair of bead parts and rubber-coated with a plurality of organic fiber cords arranged in parallel;
The carcass includes at least two carcass plies each having a main body portion extending in a toroidal manner between the bead cores for each pair of bead cores and a rewinding portion that is wound around the bead core from the inner side to the outer side in the tire width direction. A turn-up ply, and a down-ply consisting of at least two carcass plies that enclose the turn-up ply including the turn-up portion,
The organic fiber cord constituting the down ply has the following formula (I) and formula (II):
σ ≧ -0.01 × E + 1.2 (I)
σ ≥ 0.02 (II)
[Wherein σ is a heat shrinkage stress (cN / dtex) at 177 ° C .; E is an elastic modulus (cN / dtex) at a load of 49 N at 25 ° C.] .

  Here, the heat shrinkage stress σ of the organic fiber cord at 177 ° C. is obtained by heating a 25 cm long fixed sample of the reinforcing cord before vulcanization subjected to a general dip treatment at a heating rate of 5 ° C./min. The elastic modulus E of the organic fiber cord at 49N load at 25 ° C is the unit cN calculated from the tangent at 49N of the SS curve according to the JIS cord tension test. Elastic modulus at / dtex.

In a preferred embodiment of the pneumatic tire for aircraft according to the present invention, a plurality of organic fiber cords arranged in parallel between the turn-up ply located on the outermost side of the turn-up ply and the down ply are covered with rubber. A plurality of reinforcing carcass plies formed by laminating the carcass ply so that the organic fiber cords cross each other,
The reinforcing carcass ply is arranged from the outer side in the tire width direction to the bead heel part of the bead part than the outer end part in the tire width direction of the ground contact part of the tread part,
The organic fiber cord constituting the reinforcing carcass ply satisfies the conditions of the above formulas (I) and (II).

  In a preferred example of the pneumatic tire for aircraft according to the present invention, the organic fiber cord constituting the down ply is a cord of polyketone fiber. Moreover, when the pneumatic tire for aircraft of the present invention includes the reinforcing carcass ply, the organic fiber cord constituting the reinforcing carcass ply is preferably a polyketone fiber cord.

  In another preferred embodiment of the pneumatic tire for aircraft according to the present invention, the ply of the turn-up ply located on the outermost side between the turn-up ply located on the outermost side of the turn-up ply and the down ply. An interlayer rubber having a thickness in the range of 1.5 to 2 times the thickness between them is arranged. In this case, the stress due to heat shrinkage of the organic fiber cord can be relaxed.

  In another preferred embodiment of the pneumatic tire for aircraft according to the present invention, the ply of the turn-up ply located on the outermost side between the turn-up ply located on the outermost side of the turn-up ply and the down ply. Precured rubber sheets having a thickness in the range of 0.7 to 1.2 times the thickness between them are arranged.

  According to the present invention, a carcass ply in which an organic fiber cord having a specific heat shrinkage stress and elastic modulus is covered with rubber is used as a down ply constituting a carcass having a bias structure, thereby reducing the tire weight and increasing the heavy load. It is possible to provide an aircraft pneumatic tire with greatly improved durability during traveling.

  Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view of the left half of an example of an aircraft pneumatic tire of the present invention. The pneumatic tire for aircraft according to the present invention has a pair of bead portions 1 and a pair of sidewall portions 2, and a tread portion 3 connected to both sidewall portions 2, and is at least embedded in the pair of bead portions 1. Two pairs of bead cores 4 and a carcass 5 having a bias structure made of a plurality of carcass plies each extending in a toroidal shape between the pair of bead portions 1 and rubber-coated with a plurality of organic fiber cords arranged in parallel are provided. . In the illustrated tire, each bead portion 1 forms a triple bead structure in which three bead cores 4a, 4b, and 4c are embedded.

  In the pneumatic tire for aircraft according to the present invention, the carcass 5 extends from the inner side to the outer side in the tire width direction around the bead core 4 and a main body portion extending between the bead cores 4 for each pair of the bead cores 4. It comprises a turn-up ply 5a made of at least two carcass plies having a turned-up part and a down-ply 5b made of at least two carcass plies that enclose the turn-up ply 5a including the turned-up part. Here, the carcass ply constituting the turn-up ply 5a of the illustrated tire extends in a toroidal shape between the pair of bead cores 4a, 4b, 4c, and together with the carcass ply constituting the down ply 5b. The bead part 1, the side wall part 2 and the tread part 3 are reinforced. Further, the down ply 5b of the tire shown in the example is arranged so as to enclose the turn-up ply 5a including the rewinding portion, and the end portion thereof extends from the bead heel portion 6 of the bead portion 1 to the bead portion 1. Along the bead base portion 7, the bead portion 1 extends to the bead toe portion 8. Here, the bead heel portion is the innermost portion in the tire radial direction and the outermost portion in the tire width direction of the bead portion, the bead base portion is a flat portion on the innermost side in the tire radial direction of the bead portion, and the bead toe portion is The bead portion is the innermost portion in the tire radial direction and the innermost portion in the tire width direction.

  Further, the carcass ply constituting the carcass 5 of the illustrated example of the tire is preferably formed of an even number of turn-up ply 5a and down ply 5b, and the even number of carcass plies includes a plurality of parallel arranged carcass plies. The turn-up ply 5a and the down ply 5b are formed by laminating carcass plies coated with rubber on organic fiber cords so that the organic fiber cords cross each other. In the illustrated tire, since the number of carcass plies constituting the turn-up ply 5a is large, it is difficult to illustrate all the carcass plies, and these carcass plies are partially indicated by broken lines. The illustrated tire includes two carcass reinforcing layers 9 on the outer side in the tire radial direction of the crown portion of the carcass 5 having the bias structure. In the pneumatic tire for aircraft according to the present invention, the arrangement of the carcass reinforcing layers is provided. Installation is not essential, and a carcass reinforcing layer having a different structure and number of layers may be provided.

  In the carcass 5 of the aircraft pneumatic tire of the present invention, the number of carcass plies forming the down ply 5b is preferably equal to or less than the number of carcass plies forming the turn-up ply 5a. Here, when the number of carcass plies forming the down ply 5b is larger than the number of carcass plies forming the turn-up ply 5a, the water pressure resistance is lowered.

In the pneumatic tire for aircraft according to the present invention, the organic fiber cord constituting the down ply 5b is represented by the following formulas (I) and (II):
σ ≧ -0.01 × E + 1.2 (I)
σ ≥ 0.02 (II)
[Where σ is a heat shrinkage stress (cN / dtex) at 177 ° C .; E is an elastic modulus (cN / dtex) at a load of 49 N at 25 ° C.].

  When the organic fiber cord constituting the down ply 5b satisfies the conditions of the above formulas (I) and (II), the heat shrinkage stress at the high temperature of the organic fiber cord is high, so that the tire is hot during heavy load running. In this case, the rigidity of the tire is high since the initial relatively small distortion of the tire, and the radial bending rigidity of the sidewall portion of the tire is increased to suppress the deflection of the tire. As a result, the tire The durability of can be improved. In addition, when an organic fiber cord satisfying the conditions of the above formulas (I) and (II) is applied to the downply 5b, the conventional nylon cord is satisfied after satisfying the durability required for the pneumatic tire for aircraft. Compared to the case where an organic fiber cord such as the above is applied to the downply, the total number of carcass plies constituting the carcass can be reduced, and the tire weight can be greatly reduced.

  In addition, when the organic fiber cord to be used does not satisfy the relationship of the above formula (I), that is, when a cord having a large heat shrinkage stress σ but a low elastic modulus E is used, sufficient deflection of the tire during heavy load running is achieved. However, if a cord with a high elastic modulus E but a small thermal shrinkage stress σ is used, the cord will not shrink even if the tire becomes hot during heavy load running. For this reason, the radial bending rigidity of the sidewall portion of the tire does not increase. Further, if the heat shrinkage stress σ at 177 ° C. of the organic fiber cord to be used is less than 0.02 cN / dtex, the amount of deflection at the time of heavy load running becomes large, and the durability distance of the tire becomes insufficient. Further, the heat shrinkage stress σ at 177 ° C. of the organic fiber cord to be used is preferably 0.4 cN / dtex or more, but when the heat shrinkage stress σ is 1.5 cN / dtex or more, the shrinkage force during vulcanization is large. As a result, the cord inside the tire and the rubber arrangement may be disturbed, resulting in deterioration of tire durability and uniformity.

  The organic fiber cord constituting the down ply of the aircraft pneumatic tire of the present invention is preferably a polyketone fiber cord. The cord of the polyketone fiber has a reversibility that shrinks at a high temperature and expands when returned to room temperature. For this reason, the rigidity increases when the polyketone fiber cord in the down ply is contracted at high temperatures, that is, during heavy load running, and the deflection of the sidewall portion of the tire can be suppressed.

［式中、Ａは不飽和結合によって重合された不飽和化合物由来の部分であり、各繰り返し単位において同一でも異なっていてもよい］で表される繰り返し単位から実質的になるポリケトンが好ましい。また、該ポリケトンの中でも、繰り返し単位の97モル％以上が１-オキソトリメチレン［−ＣＨ₂−ＣＨ₂−ＣＯ−］であるポリケトンが好ましく、99モル％以上が１-オキソトリメチレンであるポリケトンが更に好ましく、100モル％が１-オキソトリメチレンであるポリケトンが最も好ましい。 The cord of the polyketone fiber is formed by twisting a filament bundle containing polyketone fiber, and the polyketone used as a raw material for the polyketone fiber is represented by the following general formula (III):

[Wherein, A is a portion derived from an unsaturated compound polymerized by an unsaturated bond, and may be the same or different in each repeating unit], and a polyketone substantially consisting of a repeating unit represented by Among the polyketones, polyketones in which 97 mol% or more of repeating units are 1-oxotrimethylene [—CH ₂ —CH ₂ —CO—] are preferable, and polyketones in which 99 mol% or more are 1-oxo trimethylene. Is more preferred, and a polyketone in which 100 mol% is 1-oxotrimethylene is most preferred.

  The polyketone as the raw material of the polyketone fiber may be partially bonded to each other from the ketone groups and from the unsaturated compound, but the portion of the unsaturated compound derived portion and the ketone group are alternately arranged. The ratio is preferably 90% by mass or more, more preferably 97% by mass or more, and most preferably 100% by mass.

  In the formula (III), the unsaturated compound forming A is most preferably ethylene, but propylene, butene, pentene, cyclopentene, hexene, cyclohexene, heptene, octene, nonene, decene, dodecene, styrene, acetylene. Unsaturated hydrocarbons other than ethylene such as, allene, and methyl acrylate, methyl methacrylate, vinyl acetate, acrylamide, hydroxyethyl methacrylate, undecenoic acid, undecenol, 6-chlorohexene, N-vinyl pyrrolidone, diethyl ester of sulphonylphosphonic acid , A compound containing an unsaturated bond, such as sodium styrenesulfonate, sodium allylsulfonate, vinylpyrrolidone, and vinyl chloride.

［式中、ｔ及びＴは、純度98％以上のヘキサフルオロイソプロパノール及び該ヘキサフルオロイソプロパノールに溶解したポリケトンの希釈溶液の25℃での粘度管の流過時間であり；Ｃは、上記希釈溶液100mL中の溶質の質量（g）である］で定義される極限粘度［η］が1〜20dL/gの範囲にあることが好ましく、2〜10dL/gの範囲にあることが更に好ましく、3〜8dL/gの範囲にあることがより一層好ましい。極限粘度が1dL/g未満では、分子量が小さ過ぎて、高強度のポリケトン繊維コードを得ることが難しくなる上、紡糸時、乾燥時及び延伸時に毛羽や糸切れ等の工程上のトラブルが多発することがあり、一方、極限粘度が20dL/gを超えると、ポリマーの合成に時間及びコストがかかる上、ポリマーを均一に溶解させることが難しくなり、紡糸性及び物性に悪影響が出ることがある。 Furthermore, as the polymerization degree of the polyketone, the following formula:

[Wherein, t and T are the flow times of a viscosity tube at 25 ° C. of a diluted solution of hexafluoroisopropanol having a purity of 98% or more and a polyketone dissolved in the hexafluoroisopropanol; C is 100 mL of the diluted solution It is preferable that the intrinsic viscosity [η] defined by the mass (g) of the solute in the range is 1 to 20 dL / g, more preferably 2 to 10 dL / g, and 3 to More preferably, it is in the range of 8 dL / g. When the intrinsic viscosity is less than 1 dL / g, it is difficult to obtain a high-strength polyketone fiber cord because the molecular weight is too small, and troubles such as fluff and yarn breakage occur frequently during spinning, drying and drawing. On the other hand, if the intrinsic viscosity exceeds 20 dL / g, it takes time and cost to synthesize the polymer, and it becomes difficult to uniformly dissolve the polymer, which may adversely affect the spinnability and physical properties.

  As the method for fiberizing the polyketone, (1) after spinning an unstretched yarn, performing multi-stage heat stretching, and stretching at a specific temperature and magnification in the final stretching step of the multi-stage heat stretching, (2 ) A method in which after the undrawn yarn is spun, hot drawing is performed, and the fiber after completion of the hot drawing is rapidly cooled with high tension applied. A desired filament suitable for production of the polyketone fiber cord can be obtained by fiberizing the polyketone by the method (1) or (2).

  Here, the spinning method of the unstretched yarn of the polyketone is not particularly limited, and a conventionally known method can be employed. Specifically, JP-A-2-112413, JP-A-4-228613, Wet spinning method using an organic solvent such as hexafluoroisopropanol and m-cresol as described in JP-A-4-505344, WO99 / 18143, WO00 / 09611, JP2001-164422 No., JP-A No. 2004-218189, JP-A No. 2004-285221, and the wet spinning method using an aqueous solution of zinc salt, calcium salt, thiocyanate, iron salt, etc., among these, A wet spinning method using an aqueous solution of is preferred.

  For example, in a wet spinning method using an organic solvent, a polyketone polymer is dissolved in hexafluoroisopropanol or m-cresol at a concentration of 0.25 to 20% by mass, extruded from a spinning nozzle to be fiberized, and then toluene, ethanol, isopropanol, n -Unstretched polyketone yarn can be obtained by removing the solvent in a non-solvent bath such as hexane, isooctane, acetone, methyl ethyl ketone, and washing.

  On the other hand, in the wet spinning method using an aqueous solution, for example, a polyketone polymer is dissolved in an aqueous solution of zinc salt, calcium salt, thiocyanate, iron salt, etc. at a concentration of 2 to 30% by mass, and a spinning nozzle is used at 50 to 130 ° C. Then, it is extruded into a coagulation bath and subjected to gel spinning, followed by desalting and drying to obtain an undrawn polyketone yarn. Here, in the aqueous solution in which the polyketone polymer is dissolved, it is preferable to use a mixture of zinc halide and a halogenated alkali metal salt or a halogenated alkaline earth metal salt. An organic solvent such as an aqueous solution, acetone, or methanol can be used.

  Further, as a drawing method of the obtained undrawn yarn, a hot drawing method in which the undrawn yarn is heated and drawn to a temperature higher than the glass transition temperature of the undrawn yarn is preferable. The method (2) may be carried out in one stage, but it is preferably carried out in multiple stages. There is no restriction | limiting in particular as this heat drawing method, For example, the method etc. which run a thread | yarn on a heating roll or a heating plate are employable. Here, the heat stretching temperature is preferably in the range of 110 ° C. to (melting point of polyketone), and the total stretching ratio is preferably 10 times or more.

  When polyketone fiberization is performed by the method of (1) above, the temperature in the final stretching step of the multistage thermal stretching is in the range of 110 ° C to (stretching temperature in the stretching step one step before the final stretching step-3 ° C). Moreover, the draw ratio in the final drawing step of multistage hot drawing is preferably in the range of 1.01 to 1.5 times. On the other hand, when polyketone fiberization is carried out by the method (2) above, the tension applied to the fiber after completion of the hot drawing is preferably in the range of 0.5 to 4 cN / dtex, and the cooling rate in rapid cooling is 30 ° C / The cooling end temperature in the rapid cooling is preferably 50 ° C. or lower. Here, there is no restriction | limiting in particular as a rapid cooling method of the heat-stretched polyketone fiber, A conventionally well-known method can be employ | adopted, Specifically, the cooling method using a roll is preferable. In addition, since the polyketone fiber obtained in this way has a large residual elastic strain, it is usually preferable to perform relaxation heat treatment so that the fiber length is shorter than the fiber length after hot drawing. Here, the temperature of the relaxation heat treatment is preferably in the range of 50 to 100 ° C., and the relaxation ratio is preferably in the range of 0.980 to 0.999 times.

  The manufacturing method of the organic fiber cord which comprises the down ply of the pneumatic tire for aircrafts of this invention is not specifically limited. When the organic fiber cord is formed by twisting a plurality of, preferably two or three, filament bundles of organic fibers, that is, in a double twist structure, for example, the filament bundle is subjected to a lower twist, and then It is possible to obtain a twisted cord by combining a plurality of the above and applying an upper twist in the opposite direction. Further, when the organic fiber cord is formed by twisting one filament bundle of organic fibers, that is, in a single twist structure, for example, the filament bundle of organic fibers is aligned and twisted in one direction. Thus, it can be obtained as a twisted yarn cord.

  In the pneumatic tire for aircraft of the present invention, there is no particular limitation as long as the organic fiber cord satisfying the conditions of the above formulas (I) and (II) is applied to the downply constituting the carcass. Therefore, the organic fiber cord constituting the turn-up ply of the aircraft pneumatic tire of the present invention does not have to satisfy the conditions of the above formulas (I) and (II), and is an organic fiber forming the organic fiber cord. These may be polyketone fibers or other organic fibers such as nylon fibers.

  FIG. 2 is a cross-sectional view of the left half of another example of the pneumatic tire for aircraft according to the present invention. As shown in FIG. 2, the pneumatic tire for aircraft according to the present invention includes a plurality of organic tires arranged in parallel between a turn-up ply located on the outermost side of the turn-up ply 5 a and the down ply 5 b. A plurality of reinforcing carcass plies 10 formed by laminating carcass plies in which fiber cords are covered with rubber so that the organic fiber cords cross each other may be provided. In this case, the reinforcing carcass ply 10 is preferably disposed from the outer side in the tire width direction to the bead heel portion 6 of the bead portion 1 rather than the outer end portion in the tire width direction of the ground contact portion of the tread portion 3. What is necessary is just to be arrange | positioned in at least one part between the bead heel part 6 of the said bead part 1 from the tire width direction outer side rather than the tire width direction outer side edge part of the contact part of the part 3. FIG.

  When the pneumatic tire for aircraft according to the present invention includes the reinforcing carcass ply 10, the organic fiber cord constituting the reinforcing carcass ply 10 preferably satisfies the conditions of the above formulas (I) and (II). When an organic fiber cord satisfying the conditions of the above formulas (I) and (II) is applied to the reinforced carcass ply 10, as described above, it is possible to suppress tire deflection and improve tire durability. It becomes possible to improve. Here, the organic fiber cord constituting the reinforcing carcass ply is preferably a polyketone fiber cord, similarly to the organic fiber cord constituting the down ply.

  In the pneumatic tire for aircraft according to the present invention, although not shown, an interlayer rubber and / or a precure is provided between the turn-up ply 5b located on the outermost side of the turn-up ply 5a and the down ply 5b. A rubber sheet may be arranged. Here, when the pneumatic tire for aircraft according to the present invention includes the reinforcing carcass ply 10, the turn-up ply located on the outermost side of the turn-up ply 5a and the innermost side of the reinforcing carcass ply 10 are included. An interlayer rubber and / or a pre-cured rubber sheet may be disposed between the carcass ply located at the position. Moreover, the rubber composition used for the interlayer rubber and the precure rubber sheet contains a rubber component usually used in the rubber industry, and may contain known additives such as a filler and a vulcanizing agent as necessary. In addition, the said rubber composition can be manufactured by knead | mixing a rubber component and the various compounding agents suitably selected as needed, heat-injecting, extrusion, etc.

  When an interlayer rubber is disposed between the turn-up ply 5a located on the outermost side of the turn-up ply 5a and the down-ply 5b, the interlayer rubber has a thickness between the plies of the turn-up ply located on the outermost side. It is preferable to have a thickness in the range of 1.5 to 2 times the thickness. Here, the thickness between the plies of the turn-up plies located on the outermost side is the cord distance between adjacent carcass plies in at least two carcass plies constituting the outermost turn-up ply. When the thickness of the interlayer rubber is within the above specified range, the stress due to thermal contraction of the organic fiber cord constituting the down ply can be sufficiently relaxed. In addition, when the thickness of the interlayer rubber is less than 1.5 times the thickness between the plies of the turn-up ply located on the outermost side, the stress cannot be sufficiently relaxed and separation may occur. On the other hand, if it exceeds twice, the weight of the tire increases.

  When a precure rubber sheet is disposed between the turn-up ply 5a located on the outermost side of the turn-up ply 5a and the down-ply 5b, the precure rubber sheet corresponds to the turn-up ply located on the outermost side. The thickness is preferably in the range of 0.7 to 1.2 times the thickness between the plies, and most preferably the same thickness as the thickness between the plies of the outermost turn-up ply. Here, the thickness between the plies of the turn-up plies located on the outermost side is as described above. Further, the precure rubber sheet is a rubber sheet that has undergone a pre-vulcanization treatment, and by disposing the rubber sheet, it is possible to suppress the flow during the vulcanization molding of the rubber constituting each carcass ply. In addition, when the thickness of the precure rubber sheet is within the above specified range, the stress due to the thermal contraction of the organic fiber cord constituting the down ply can be sufficiently relaxed.

  In the pneumatic tire for aircraft according to the present invention, for example, an organic fiber cord satisfying the above formulas (I) and (II) is applied to the down ply 5b, preferably a polyketone fiber cord, and the turn-up ply 5a is made of nylon. An organic fiber cord that is usually used for a carcass such as a cord is applied, and preferably, at least one of a reinforcing carcass ply 10, an interlayer rubber, and a precure rubber sheet is disposed, and the cord can be produced by a conventional method. Here, there is no restriction | limiting in particular as coating rubber | gum of a code | cord, The coating rubber used for the conventional carcass ply can be used. Prior to the rubber coating of the cord, the cord may be subjected to an adhesive treatment to improve the adhesion to the coating rubber. Furthermore, it is preferable to apply an organic fiber cord, preferably a polyketone fiber cord, that satisfies the conditions of the above formulas (I) and (II) to the reinforcing carcass ply. In the pneumatic tire for aircraft according to the present invention, as the gas filled in the tire, normal or air having a changed oxygen partial pressure, or an inert gas such as nitrogen can be used.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.

A pneumatic tire for aircraft having a structure shown in Table 1 and having a tire size: H49 × 19.0-22 32PR was manufactured according to a conventional method. Further, the number of carcass plies constituting the turn-up ply, the down ply and the reinforcing carcass ply, the material and number of driving of the organic fiber cord forming the carcass ply, and the thickness between the plies of the turn-up ply located on the outermost side Table 1 shows the ratio of the thickness of the interlayer rubber (not shown) with respect to the thickness and the thickness between the plies of the outermost turn-up plies. When the organic fiber cord forming the carcass ply is a nylon fiber cord, the cord has a fineness of 1400 dtex / 2, a heat shrinkage stress σ at 177 ° C. of 0.2 cN / dtex, and a load of 49 N at 25 ° C. The elastic modulus E at the time is 40 cN / dtex. On the other hand, when the organic fiber cord forming the carcass ply is a polyketone fiber cord, the fineness of the cord is 1400 dtex / 2, the heat shrinkage stress σ at 177 ° C. is 0.5 cN / dtex, and the load is 49 N at 25 ° C. The elastic modulus E at the time is 155 cN / dtex. In the polyketone fiber used, 98% of the repeating units are (CH ₂ —CH ₂ —CO).

  Next, the durability of the tire during heavy load running was evaluated on the produced tire by the following method. The results are shown in Table 1.

(1) Durability of tires during heavy loads
Under the action of 1.2 times the normal load specified in THE TIRE AND RIM ASSOCIATION YEAR BOOK, it is filled with 205 psi of internal pressure, runs at a speed of 60 km / hr for 10 minutes, and repeats a test cycle of 2 hours. The number of times until failure occurred was measured. Here, the number of times until the failure of the tire of the conventional example occurred was expressed as an index. The larger the index value, the better the durability of the tire during heavy load running.

  From Table 1, since the tire of the example uses an organic fiber cord that satisfies the conditions of the above formulas (I) and (II) for the downply 5b, the tire of the example is more durable at the time of heavy load running than the conventional tire. It turns out that it is excellent. Further, it can be seen that the tire of Example 2 provided with the reinforced carcass ply has further improved durability during heavy load traveling than the tire of Example 1. In addition, since the total number of carcass plies constituting the tire of Example 1 is smaller than the total number of carcass plies constituting the conventional tire, the tire of Example 1 maintains excellent durability during heavy load running. It can be seen that the tire weight can be reduced.

It is sectional drawing of the left half of an example of the pneumatic tire for aircrafts of this invention. It is sectional drawing of the left half of the other example of the pneumatic tire for aircrafts of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bead part 2 Side wall part 3 Tread part 4, 4a, 4b, 4c Bead core 5 Carcass 5a Turn-up ply 5b Down ply 6 Bead heel part 7 Bead base part 8 Bead toe part 9 Carcass reinforcement layer 10 Reinforced carcass ply

Claims (5)

A pair of bead portions, a pair of sidewall portions, and a tread portion connected to both sidewall portions, at least two pairs of bead cores embedded in the pair of bead portions, and a toroid shape between the pair of bead portions In a pneumatic tire for an aircraft equipped with a carcass having a bias structure composed of a plurality of carcass plies each extending in parallel and rubber-coated with a plurality of organic fiber cords arranged in parallel,
The carcass includes at least two carcass plies each having a main body portion extending in a toroidal manner between the bead cores for each pair of bead cores and a rewinding portion that is wound around the bead core from the inner side to the outer side in the tire width direction. A turn-up ply, and a down-ply consisting of at least two carcass plies that enclose the turn-up ply including the turn-up portion,
The organic fiber cord constituting the down ply has the following formula (I) and formula (II):
σ ≧ -0.01 × E + 1.2 (I)
σ ≥ 0.02 (II)
[Wherein σ is a heat shrinkage stress (cN / dtex) at 177 ° C .; E is an elastic modulus (cN / dtex) at a load of 49 N at 25 ° C.] Pneumatic tire for aircraft. Between the turn-up ply located on the outermost side of the turn-up ply and the down ply, the organic fiber cords cross each other in a carcass ply in which a plurality of organic fiber cords arranged in parallel are covered with rubber. A plurality of reinforcing carcass plies formed by stacking,
The reinforcing carcass ply is arranged from the outer side in the tire width direction to the bead heel part of the bead part than the outer end part in the tire width direction of the ground contact part of the tread part,
The organic fiber cord constituting the reinforcing carcass ply has the following formulas (I) and (II):
σ ≧ -0.01 × E + 1.2 (I)
σ ≥ 0.02 (II)
[Wherein σ is a heat shrinkage stress (cN / dtex) at 177 ° C .; E is an elastic modulus (cN / dtex) at a load of 49 N at 25 ° C.] The pneumatic tire for aircraft according to claim 1.   The pneumatic tire for aircraft according to claim 1, wherein the organic fiber cord is a cord of polyketone fiber.   Between the turn-up ply located on the outermost side of the turn-up ply and the down ply, a thickness in the range of 1.5 to 2 times the thickness between the plies of the turn-up ply located on the outermost side. The pneumatic tire for aircraft according to claim 1, wherein an interlayer rubber is provided.   Between the turn-up ply located on the outermost side of the turn-up ply and the down ply, a thickness in the range of 0.7 to 1.2 times the thickness between the plies of the turn-up ply located on the outermost side. The pneumatic tire for aircraft according to claim 1, wherein a precure rubber sheet is disposed.

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