JPH0268207A - Radial tire for heavy load and high speed - Google Patents

Abstract

PURPOSE:To prevent damage of an outer ply cord which is subjected to the largest compression distortion by a method wherein the number of twistings of the outer ply is larger than that of an inner layer in a carcass having an inner layer composed of inner plies and an outer layer composed to outer plies. CONSTITUTION:In a carcass 7 having an inner layer 7A composed of a plurality of inner plies 7a where a bead core 2 is folded from the inside toward the outside of a tire and an outer layer 7B composed of a plurality of outer plies 7b where said folded portion is wounded down from the exterior of the tire into the inner, the respective carcass cords are provided in radial directions tilted 70 to 90 deg. with respect to a tire equator. At this time, with the number of twistings per unit length of the carcass cord of the outer ply 7b made larger than that of the inner play 7a, elasticity of the outer ply 7b is smaller than that of the inner ply 7a and load extension and breaking extension are made larger so that strength in compression is increased, preventing a cord from breaking.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a heavy-duty, high-speed radial tire that can improve the durability of the bead portion and can be particularly suitably used as an aircraft tire.

[Conventional technology]

Heavy-duty, high-speed radial tires, especially aircraft tires used for aircraft, have increased in size and flight speed in recent years, resulting in increased speeds and loads during takeoff and landing. The amount of deflection in the tire radial direction under load is set to be relatively large, for example, about 28 to 35%, so the aircraft tire is
For safe takeoff and landing, it is necessary to withstand repeated large deformations, large loads, and high speeds.

On the other hand, as such aircraft tires, those having a cross-ply structure in which carcass cords are arranged so as to cross each other between plies are often used.

However, the rigidity of the tread part is low and the weight of this type is large, which makes it unfavorable in terms of wear resistance and heat generation. There are limits to its use.

Therefore, in recent years, radial tires have been developed that have a so-called radial structure carcass in which carcass cords are arranged in the tire radial direction, and a bell (made of a highly elastic belt cord) 71 that is inclined at a small angle with respect to the tire equator is arranged on the outside in the radial direction of the carcass. It is being used.

[Problem to be solved by the invention]

However, as the life of such radial structure aircraft tires increases, it has been found that the durability of the bead portion in particular is relatively low compared to the durability of the tire as a whole.

On the other hand, tires with a radial structure have a characteristic due to their structure, such as the provision of a strong belt, and the deformation of the tread is small. Therefore, the deformation of the sidewall portion and bead portion is large compared to radial tires in other fields and even compared to bias structure aircraft tires.

In particular, the bead apex, which is made of rubber that has relatively high hardness and generates a large amount of heat due to deformation, is placed in the bead section, so the heat generated by repeated deformation during takeoff and landing operations causes high temperatures, and the bead The department is
Since the thickness is large and the carcass winding portion, reinforcing layer, etc. are concentrated, shear strain occurs at the bead portion due to bending deformation, resulting in t-shell scratches on the tire.

Regarding the durability of the bead portion, when the amount of radial deflection of the tire under load is large, about 28 to 35%, as described above, the carcass cord of carcass A has the following characteristics, as shown in FIG. It is clear that compressive stress acts on the portion folded around the bead core B, and tension that pulls the carcass cord is generated on the inner side in the axial direction of the tire.

On the other hand, it has been found that damage to the bead portion occurs near the rim flange C side. This is due to the compression caused by the sudden bending above the rim flange C, which causes compressive stress concentration to occur in that part, and also causes a large compressive stress in the carcass cord in that part, which also causes compressive strain in the carcass cord. to occur. Further, the carcass cord is broken due to fatigue as the compressive stress is repeated, and the cut end causes local concentration of the compressive stress. The drum test results revealed that such repeated compressive stress reduces the strength of the carcass cord as well as the rubber itself, causing damage to the bead.

Therefore, in order to solve these problems, the present inventors proposed a method near the rim flange, which consists of an inner layer that folds the carcass around the bead core from the inside of the tire to the outside, and an outer layer that is rolled down outside the bead core. In addition to increasing the compressive strength of the ply and eliminating the separation that tends to occur at the tip of the winding part of the inner layer, the number of twists per unit length of the carcass cord of the ply forming the outer layer is greater than that of the inner layer ply. It was realized that the compressive strength of the outer ply could be further increased by forming the bead part in this way, and the durability of the bead part was increased and the scales were confirmed by forming it in this way.

The present invention is based on the fact that the carcass consists of two layers, an inner layer and an outer layer, and that the number of twists of the outer ply cord forming the outer layer is larger than that of the inner layer, thereby improving the durability of the bead portion and increasing the hanging weight. The purpose is to provide high-speed load-bearing radial tires.

[Means to solve the problem]

The present invention has a carcass cord of 70 to 70 mm with respect to the tire equator.
An inner layer consisting of at least one inner ply arranged side by side at an angle of 90 degrees and having a folded part for folding the bead core from the inside to the outside of the tire in a toroidal main body part, and an 8-inch inner ply PAIRed on the outside of the main body part. A carcass having a toroidal main body and an outer layer consisting of at least one outer ply having an unrolled part wound down outside the bead core and a belt cord are arranged side by side at an angle of 0 to 20 degrees with respect to the tire equator. a belt layer consisting of a plurality of plies, and the number of twists per unit length of the carcass cord of the outer ply is greater than the number of twists per unit length of the carcass cord of the inner ply. It is a radial tire.

[Effect]

As described above, in the heavy-duty high-speed radial tire of the present invention,
By making the number of twists per unit length of the carcass cord of the outer ply forming the outer layer of the carcass larger than that of the inner ply of the inner layer, the outer ply has a lower modulus of elasticity than the inner ply, and the outer ply has a lower elastic modulus than the inner ply. Since the elongation and elongation at break are greater than that of the inner ply, the compressive strength of the outer ply increases, thereby preventing the cord from breaking and increasing the durability of the bead portion.

〔Example〕

An embodiment of the present invention will be described below with tire size 46×17R20.
This will be explained based on the drawings, taking as an example the case of an aircraft tire.

In FIG. 1 showing a state filled with the normal internal pressure, the high-speed radial tire 1 has a bead portion 3 through which a bead core 2 passes;
The tire includes a sidewall part 4 connected to the bead part 3 and extending outward in the tire radial direction, and a tread part 5 connecting the outer ends of the sidewall part 4.

Furthermore, the tire l has a plurality of inner plies 7, for example, four inner plies 7, which fold the bead core 2 from the inside of the tire to the outside.
an inner layer 7A consisting of a-, and a plurality of outer plies 7b, for example two outer plies 7b, which surround the folded portion of the inner layer 7A and are wound down from the outside to the inside of the tire.

A carcass 7 is provided having an outer layer 7B consisting of 7b.

The inner carcass blur f7a has side oar parts,
The main body part 70 that passes through the tread part and has a wide shape has a folded part 71 that folds the bead core 2 from the inside to the outside of the tire, and the outer ply 7b has a toroid-like main body part 73.
The bead core 2 is provided with an unrolling part 74 unrolled outside the bead core 2.

- The carcass cords of the inner puller r1a and the outer ply 7b are arranged in the radial direction with an inclination of 70 degrees to 90 degrees with respect to the tire equator, and in this example, the carcass 7 is arranged between adjacent carcass plies The cords alternately intersect and are inclined in the tire radial direction.

The carcass cord of the outer ply 7b weighs 5 kg.
An elastic cord having an elongation of 6 to 10% under a load of f and 11 to 15% under a load of 10 kgf is used, and such an elastic cord has a curve a shown in FIG.

It has characteristics in the range between b. For curve a, the load at break, that is, the cord strength, is usually 55 kg.
The cord strength is about f and the curved one has a cord strength of 40
It is about kg f. Furthermore, as is clear from the songs 'vAa and b, the elastic cord has the characteristic that it elongates greatly when a small load is applied, and that the elongation rate decreases as the load increases, and the elongation at break is It is set to 28% or less. In addition, as shown by curve C for the conventional chord, song N
It can be seen that the rise is large and substantially linear compared to IAa.

Further, as the elastic cord, a nylon cord, a polyester cord, an aromatic polyamide cord, a carbon cord, a metal cord, or a hybrid cord of two or more kinds of cords is used.

Furthermore, when using a cord with such physical properties, the tension in so-called depth stretching, in which tension and heat are applied to the cord for a predetermined period of time, is lower than the tension used in conventional depth stretching. It can be obtained by reducing it to a large amount. In order to improve this characteristic, the number of ffl twisted per 10a1m was increased to 2.
9-40 T/103.

More preferably, it is 32 to 36T/103, which increases the number of twists compared to about 23 to 28T/10 (about J), which is conventionally done. When the load reaches a predetermined value, the load is applied to the cord with a small elongation, and the elongation rate decreases as a whole. It can also be formed.

Also, the carcass cord of the inner ply 7a uses an elastic cord like the carcass cord of the outer ply 7b, but its characteristics are that the elongation under a 5-f load is 6.
%, and the elongation at 10 kgfVI weight is set to less than 11%.

Furthermore, the number of twists per l0CII of the inner ply 7a is 257/10 or less, which is smaller than that of the outer ply 7b.

In this way, by making the number of twists per unit length of the carcass cord of the outer ply b larger than that of the inner ply, the compressive stress applied to the outer ply 7b is resisted and breakage of the cord of the outer ply 7b is prevented. be able to.

Further, a coating layer 8 is provided on the inner surface of the carcass 7 to prevent wear and tear of the carcass 7, which moves in a spiral manner around the bead core 2 as the tire is repeatedly deformed. A bead apex 9 made of tapered rubber extending beyond the upper end of the covering 1118 is provided to disperse stress by bending the carcass folded portion. Bead Apex 9 has a lower f! It consists of a lower part 9A made of rubber and an upper lower part 9B made of soft rubber, and a chafer (not shown) for preventing rim displacement may be provided on the outer surface of the bead part 3. Note that as the bead apex 9, relatively hard rubber having a JISA hardness of 65 to 95 degrees can be suitably used.

Further, the tread portion 5 is provided with a belt layer 10 inside thereof located outside the carcass 7 in the radial direction, and in this example,
A cut breaker 14 is interposed between the belt layer 10 and the carcass 7.

Further, the belt layer 10 may include a plurality of belt plies 10, for example four belt plies 10. ) and the cut breaker 1
4, and a plurality of belt plies, for example, four belt plies 10b, located radially outside of the inner WJ1 OA.
and an outer layer 10B consisting of.

The cut breaker 14 uses, for example, two layers of cut breaker plies 14a, 14a, while the cut breaker 14 extends along the carcass 7 and at the crown portion 20, which is the center of the trend plane across the tire equator. , gradually separates from the carcass 7 on the outside, and its outer end ends at a position in the range of about 70 to 85%, preferably about 73 to 78%, of the tire hit W.

Furthermore, the inner layer 10B of the belt layer 10 is in contact with the cut breaker 14 in the range of the crown portion 20 and is slightly spaced apart, while its outer end has a width WI OA extending outwardly beyond the outer end of the cant breaker 14. have The outer edge is within a range of about 75 to 85% of the tire hit W, and is the shortest path 11 to the tire outer surface S! The ILI is set to be in the range of about 3 to 8B.

The outer layer 10B of the belt layer 10 is in contact with the inner layer 10A, and its outer end is located between the outer end of the cut breaker 14 and the outer end of the inner layer 1110A, so that the outer end and the tire outer surface are in contact with each other. 75 to 80 of the tire width W, keeping the distance L2 between the tire
The width WIOB is set in the range of %.

Note that the width of the cut breaker 14 may be larger than the width WIOB of the outer layer 10B, or even larger than the width WIOB of the inner layer 10A.
The width of WIOA can also be made larger than that of WIOA.

Further, the belt cords forming the belt plies 10a, 10b are made of highly extensible elastic cords, and the belt cords are arranged side by side at an angle of 0 to 20 degrees with respect to the tire equator.

In this way, by giving a larger elongation to the carcass ply 7b of the outer Ji7B than in conventional tires, the compressive stress of the carcass cord generated on the rim flange C side is reduced when the bead portion 3 is bent during takeoff and landing. Since compressive strain can be reduced, deformation, local bending, and even fatigue due to compressive strain (cutting, etc.) can be prevented.Furthermore, the compressive stress of the rubber itself of the bead portion 3 can be balanced out. Therefore, the durability of the bead portion can be improved by, for example, more than 10%.

Moreover, as mentioned above, the elongation of elastic cords decreases as the load increases.Since such elastic cords form the carcass cord and belt cord 11, the tread that tends to occur in tires rotating at high speeds This prevents so-called tire growth, in which the outer shape of the crown section, in particular, permanently expands.

Cords made of different materials may be used as the cut-off breaker cord and belt cord as long as they have similar characteristics.

Further, both the belt cord 11 and the carcass cord are relatively thick cords with a diameter dll, for example, 1260 d/
A code of about 2 to 2700 d/3 is used.

Furthermore, the carcass cord and belt cord 11 are embedded in the base rubber to form the carcass plies 7a, 7b.
, forming belt plies 10a, 10b. This base rubber has a JISA hardness of 60 to 90 degrees, a 100% modulus of 30 to 60 kg/ci, and a stress at break of 150 degrees.
~300kirf/cd, elongation at break 300~6
Uses rubber with excellent durability.

By using rubber with such characteristics as the base material rubber, the carcass cord and belt cord 11 can be easily stretched, and pretension can be applied to the bead portion, and the tread portion 5 can be easily stretched.
In addition to facilitating the above-mentioned expansion, the large elongation at break increases the durability of the bead portion and prevents the occurrence of standing waves.

Note that the cut breaker ply 14a has the same configuration as the belt plies 10a and 10b.

Furthermore, by attaching the green ply in which the belt cord 11 is embedded in the base rubber so that the belt cord 11 is inclined at an angle of 0 to 20 degrees with respect to the tire equator, the belt plies 10a, 10b are is formed.

Note that the belt N10 can have an inclination angle reversed between the inner layer III OA and the outer layer 10B, or can change the inclination for each ply 10a and 10b.

Furthermore, the bell l-7110 can also be formed as an endless type by a so-called cord winding method in which one or several cords are wound helically.

Further, the cut breaker cord of the cut breaker ply 14a is attached with an inclination of 10 to 30 degrees.

FIG. 3 shows another embodiment in which an auxiliary belt layer 12 is arranged on the radially outer side of the belt rfi 10.

The auxiliary belt) 1112 is one auxiliary belt ply 1
2a, and the ratio of the width W12 of the auxiliary belt layer 12 to the maximum weight of the belt layer 10, that is, the width WIOA of the inner layer 10A, is set in the range of 0.10 to 0.35. Further, the outer end of the auxiliary belt layer 12 is connected to the belt layer 1.
In the vicinity of the outer end of 0, in this example, it coincides with the outer end of the outer 1110B. The inner end of the auxiliary belt layer 12 thus extends inwardly beyond the crown portion 2°.

Also, the auxiliary belt cord 13 of the auxiliary belt ply 12a is
It has a narrow diameter d13 such that the ratio to the diameter dll is 0.20 to 0.50. That is, the auxiliary belt cord 13 has a thickness of approximately 300 to 1350 d/3 and is within the above ratio range.

Further, when the auxiliary belt ply 12a is attached to the uppermost belt ply 10b of the belt layer 10, as shown in FIG. The thickness of the base rubber is adjusted so that the distance 1IL3 between the radially inward end of the belt cord 13 and the radially outward end of the belt cord 11 is 0.2 to 1.0. It is formed to be slightly thicker than the diameters d11 and d13 of the cords 11 and 13.

Furthermore, when such an auxiliary belt [12 is used, each of the plies 10a, 10b.

12a, the cord density, i.e. the plies 10a, 10b in a direction perpendicular to the longitudinal direction of the cord;
The ratio between the reference length l of 12a and the sum of diameters Σd11 and Σd13 of the cords 11.13 included within this reference length β, Σ
dll/JX100, Σd13/! X100 is in the range of 50 to 85% in the case of the belt layer 10 and 35 to 65% in the case of the auxiliary belt 1112, and in addition, the auxiliary belt layer 12
The cord density of the belt W110 is set to be smaller than the cord density of the belt W110 by a ratio of 0.35 to 0.8.

In addition, the auxiliary belt cord 13 is 0 to 0 with respect to the tire equator.
Attach at a 20 degree angle.

The auxiliary belt layer 12 has lower rigidity and greater extensibility than the belt layer 10.

Therefore, the tension when filling the internal pressure is borne by the belt layer 10 together with the carcass 7, and the auxiliary bell) J
112 is interposed between the belt layer 10 and the tread portion 5, so that the difference in rigidity between the belt layer 10 and the tread portion 5 can be alleviated.

As a result, the shear stress generated between the tread rubber and the belt layer 10 during internal pressure filling and ground contact can be alleviated by the contribution of the auxiliary belt layer 12.

As shown in FIG. 5, an auxiliary belt layer 12 having such a function can be provided on the entire surface of the belt Ni10, or as shown in FIG. belt layer 1
0 may be used in combination with the auxiliary belt ply 12b covering the belt.Also, as shown in FIG.
It is also possible to provide two auxiliary belt plies 12a, 12a.

(Example) A tire of Tire Nize 46X17R20 having the structure shown in FIG. 1 was manufactured as a prototype according to the specifications shown in Table 1.

In addition, tires shown in the comparison column were manufactured, filled with the standard internal pressure, loaded with 200% of the standard load, and at a circumferential speed of 30.
A rotation test was conducted at 0 @/h and the durability of the bead portion was compared and the results are shown in Table 1.

The time required for one scratch on the bead portion is shown as 100 for the comparative example. It can be seen that the implemented product has a 15% improvement compared to each comparative product.

〔Effect of the invention〕

As described above, in the heavy-duty radial tire of the present invention, the carcass is formed by the inner layer consisting of the inner ply and the outer layer consisting of the outer ply, and the number of twists per unit length of the carcass cord of the outer ply is higher than that of the inner ply. This makes it possible to prevent damage to the outer ply cord, which is subject to the largest compressive strain during tire deformation, and improve the durability of the bead portion.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing one embodiment of the present invention, FIG. The figure is a sectional view illustrating the belt ply and the auxiliary belt ply, FIGS. 5 to 7 are sectional views illustrating other examples of the auxiliary belt ply, and FIG. 8 is a line diagram illustrating tire deformation. 2-Bead core, 3-Bead portion, 4-Side wall portion, 5-Tread portion, 7
- Carcass, 7A--Inner layer, 7B--Outer layer, 7a-Inner ply, 7b-Outer ply,
10-belt layer, 70-main body part, 7 73-main body part,

Claims (1)

[Claims] 1. The carcass cord is set at 70 to 90 degrees with respect to the tire equator.
an inner layer consisting of at least one inner ply that is tilted and juxtaposed and has a folded part for folding a bead core from the inside to the outside of the tire in a toroidal main body; and a toroidal main body that is adjacent to the outside of the main body of the inner ply. A carcass having an outer layer consisting of at least one outer ply having an unrolled part wound down outside the bead core and a belt cord made of a plurality of plies arranged side by side at an angle of 0 to 20 degrees with respect to the tire equator. A heavy-load, high-speed radial tire comprising: a belt layer having a belt layer, and the number of twists per unit length of the carcass cord of the outer ply is greater than the number of twists per unit length of the carcass cord of the inner ply. 2. The heavy-duty high-speed radial tire according to claim 1, wherein the number of twists of the carcass cord of the outer ply is 29 to 40T/10cm, and the number of twists of the carcass cord of the inner ply is less than 29T/10cm. . 3 The carcass cord of the outer ply is 5kgf.
The elongation under load is 6 to 10%, the elongation under 10 kgf load is 11 to 15%, and the inner ply carcass cord has an elongation of less than 6% under 5 kgf load, and less than 11% under 10 kgf load. The heavy-duty high-speed radial tire according to claim 1 or 2, characterized in that: