JP3231911B2 - Aircraft tires - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire for aircraft used in aircraft.

[0002]

2. Description of the Related Art A pneumatic tire dedicated to an aircraft is used in an aircraft. A large number of pneumatic tires are used in aircraft, and these pneumatic tires are required to have improved wear resistance, an increased number of times of rehabilitation, reduced weight, durability, reduced space, and the like.

[0003] In order to maintain the durability of a pneumatic tire, it is necessary to minimize damage caused by a tire cut due to foreign matter during traveling on a runway. Here, a protective layer is buried in the tread portion of the tire, and the protective layer prevents the cut from the outside from proceeding to the belt. This protective layer is composed of a plurality of wavy aramid cords, and these aramid cords are arranged at predetermined intervals in the tire width direction, and each extends along the circumferential direction of the tire.

[0004] In the pneumatic tire provided with the protective layer as described above, the progress of the cut to the belt was prevented, and the tire life related to the cut could be extended.

[0005]

However, the provision of the above-mentioned protective layer causes a crack to occur between the aramid cords of the protective layer, and the crack propagates to the bottom of the groove to generate a groove crack. occured. In order to enhance the effect of preventing the cut from progressing to the belt, it is effective to reduce the pitch size of the aramid cord of the protective layer. The investigation revealed that cracks occurred in the layer.

In view of the above, an object of the present invention is to provide an aircraft pneumatic tire that can reliably prevent the occurrence of groove cracks while maintaining the effect of preventing the cut from progressing to the belt.

[0007]

An aircraft pneumatic tire according to the present invention is provided with a toroidal carcass, a tread portion provided on a crown portion of the toroidal carcass and in contact with a road surface, and a tread portion provided on the tread portion. A plurality of land portions divided by a plurality of circumferential grooves extending along the circumferential direction, and a non-stretchable cord embedded in the base of the tread portion and extending substantially in a sine curve along the tire circumferential direction. A reinforcing layer formed by arranging a plurality of the non-shrinkable cords in the tire axial direction, wherein the driving density of the non-shrinkable cord is lower in the area corresponding to the circumferential groove than in the area corresponding to the land. It is characterized by having a density.

[0008]

According to the aircraft pneumatic tire of the present invention, the driving density of the non-stretchable cord forming the protective layer buried in the tread portion corresponds to the circumferential groove with respect to the area corresponding to the land portion. By reducing the density of the area, the shearing force of the rubber layer between the cords in the area corresponding to the groove of the protective layer is reduced, and the occurrence of cracks in the rubber layer between the cords in this area is prevented. Generation can be prevented.

[0009]

FIG. 2 shows an aircraft pneumatic tire 10 according to this embodiment. In the tire 10, a pressure vessel is formed by a carcass 12 that maintains an internal pressure of air supplied inside. The carcass 12 has a horseshoe shape, industrial fibers (for example, nylon, polyester, aramid, and the like), and in some cases, a plurality of cords formed of steel wires are arranged, and the cords are covered with a rubber layer. . Carcass 1 of tire 10 of the present embodiment
The cord applied to 2 is a nylon fiber.

The tire 10 of the present embodiment has a radial structure in which the axial direction of the cords of the carcass 12 is along the width direction of the tire 10, and these cords are arranged in the circumferential direction of the tire 10.

The surface of the carcass 12 is covered with a rubber layer 14. The rubber layer 14 has side surfaces of the tire 10 shown in FIG. 1 called side walls 16, and has a role of protecting the outside of both side walls of the carcass 12.

Both ends of the carcass 12 are wound around and held by beads 18 having a ring shape around the rotation axis of the tire. The bead 18 is also covered with the rubber layer 14 and constitutes a bead portion 20 as a whole. The bead portion 20 determines the size of the inner circumference of the tire 10 and secures fitting with a rim (not shown).

The upper part of the rubber layer 14 in FIG. The tread portion 22 is a portion that is actually in contact with the ground, and is thick enough to withstand abrasion and external damage.

The cords 2 arranged between the carcass 12 and the tread portion 22 at an angle close to the circumferential direction of the tire 10 (normally about ± 16 ° when the circumferential direction of the tire 10 is 0 °).
4 (see FIG. 3) are arranged in layers so that adjacent belts 26 are covered with a rubber layer. The rigidity of the tire 10 is maintained by the belt 26.

As shown in FIG. 2, the tread portion 22 has
A plurality of (four in this embodiment) grooves 28 extending in the tire width direction are formed at predetermined intervals in the tire width direction, and land portions 29 extending in the circumferential direction are formed by these grooves 28.
Is partitioned. These grooves 28 have a role of releasing heat generated in the tire 10 in addition to drainage and design elements.

As shown in FIGS. 2 and 3, the tread portion 2
2, a protective layer 30 as a reinforcing layer is embedded at a distance from the tread side of the uppermost layer of the belt 26. Protective layer 30
Is a tread in which corrugated industrial fiber cords (aramide cords 32 in the present embodiment) are arranged along the width direction (arrow W direction) of the tire 10 and covered with a rubber layer, and are damaged by ground contact with the ground. It has a function of protecting the progress of cutting from the surface of the portion 22 from being transmitted to the belt 26. The width of the protective layer 30 is preferably equal to or slightly smaller than the tread width.

As shown in FIG. 1, in the protective layer 30, the pitch of the aramid cord 32 is different between the area corresponding to the land 29 and the area corresponding to the groove 28.

In the protective layer 30, the pitch L (mm) of the aramid cord 32 in the area corresponding to the land portion 29 and the diameter d (mm) of the aramid cord 32 are expressed by the following equation (1). preferable.

[0019]

(Equation 1)

Here, Ld: spacing dimension between cords R: porosity of the area corresponding to the land.

On the other hand, the pitch dimension L of the aramid cord 32 in the area corresponding to the bottom of the groove 28 and the aramid cord 32
Is preferably in a relationship of the following Expression 2.

[0022]

(Equation 2)

Here, L'-d: the spacing between cords at the position corresponding to the bottom of the groove S: the porosity of the area corresponding to the bottom of the groove Also, the distance from the bottom of the groove 28 to the aramid cord 32 H preferably has the following relationship.

H ≧ 2 mm (2) The diameter d of the aramid cord 32 is d = 0.65 to 0.65.
It is preferable that the thickness of the tire 1 is 1.2 mm.
The diameter d of the aramid cord 32 used at 0 is 0.7 mm
(1500d / 2).

In this embodiment, the aramid code 32
Extend substantially in a sine curve along the circumferential direction of the tire, and have a wavelength A of 26 mm and an amplitude λ of 7 mm (see FIG. 3).

R _min / S _max × 100 = 25% or more
Preferably, it is 60%. In this case, L _max -d needs to be about 1.05 mm, and L _min -d needs to be about 0.23 mm.

Here, the position of S _{max is} a position substantially corresponding to the center of the groove 28 in the width direction, R _min is a position corresponding to substantially the center of the land portion 29 in the width direction, and the porosity is gradually between R _{min and} S _max. Change.

Further, the position of the protective layer 30 is preferably substantially at the center between the bottom of the groove 28 and the back surface of the tread portion 22 (the outermost surface of the belt 26 in the tire radial direction) or slightly closer to the belt 26. In this embodiment, the distance H from the bottom of the groove 28 to the protective layer 30 is 2.5 mm, and the dimension T from the outermost surface in the tire radial direction of the belt 26 to the protective layer 30 is 2.5 mm (see FIG. 1). Here, between the belt 26 and the protective layer 30, the rubber or the protective layer 3 constituting the tread portion 22 is provided.
It is preferable to use a rubber similar to the coating rubber applied to zero.

The operation of this embodiment will be described below. When the tread portion 22 of the tire 10 is damaged while the aircraft is traveling on the runway or the guideway, the surface of the tire 10 is cut. If the running is continued in this state, the cut advances toward the center of the tire 10.

Here, when the surface of the land portion 29 of the tread portion 22 is cut, the progress of the cut is minimized because the tread portion 22 has a sufficient thickness.

On the other hand, when the bottom of the groove 28 of the tread portion 22 is cut, if the distance H between the bottom and the protective layer 30 is not sufficient, the cut proceeds to the protective layer 30 and causes peeling. However, in this embodiment, this distance H is 2 mm
Since the above is one of the conditions for manufacturing the tire 10, the progress of the cut generated at the bottom of the groove 28 in the direction of the protective layer is prevented.

The protective layer 30 has a porosity R of 60% or less in a region corresponding to the land portion 29 and a porosity S of 70% or less in a region corresponding to the groove 28, thereby providing grounding to the road surface. The original function of the protective layer 30 that does not transmit the progress of the cut from the damaged surface of the tread portion 22 to the belt 26 is maintained.

Here, when the protective layer 30 is manufactured without determining the minimum porosity level, a large shear force acts between the aramid cords 32, and cracks occur in the rubber layer between the aramid cords 32. . However, in this embodiment, the minimum level of the porosity R in the area corresponding to the land 29 is 25%.
If so, the aramid code 32 in the area corresponding to the land 29
Cracks can be prevented from occurring in the rubber layer between them.

Further, in the tire 10 of the present embodiment, the porosity S of the area corresponding to the groove 28 of the protective layer 30 is set to be larger than the porosity R of the area corresponding to the land portion 29. The generation of cracks from the area corresponding to the groove 28 of the groove 30 is highly prevented, and the generation of groove cracks can be reliably prevented, so that the durability of the tire 10 can be further increased as compared with the related art.

In this embodiment, the effect of setting the distance H between the bottom of the groove 28 and the protective layer 30 to 2 mm or more and the effect of setting the porosity R and S within a predetermined range will be separately described. However, these set values are interrelated, and when applied to an aircraft pneumatic tire for which weight reduction is desired, the distance H is set to the minimum value (2 mm), and the optimum porosity R, It is preferable to define S.

(Test Example) A tire to which the present invention was applied and a comparative tire in which the cord interval of the protective layer was constant were prototyped, and the effect of preventing groove cracking (GC) and the effect of preventing cut growth were examined for each tire. The results are shown in Table 1 below.

The groove crack test and the cut growth test were performed using a drum tester (room temperature: 20 ° C.) equipped with a steel drum having a smooth surface and a diameter of 3.048 mm.

Test tire (tire size: 30 × 8.8)
In R15), a knife wound having a circumferential length of 20 mm and a depth of 1 mm was previously formed at the bottom of the groove, and the internal pressure was 14.3 kg / cm ² (normal internal pressure), the load was 5200 kg (normal load), and the running speed was 64 mm.
After running at km / h for 10 minutes, the vehicle was stopped for 50 minutes, and after repeating this 800 times, the number of groove cracks (GC) generated in the circumferential direction was counted, and the crack length that grew in the circumferential direction from the knife scratch was measured. It was measured.

[0039]

[Table 1]

From the results shown in Table 1 above, it can be seen that the aircraft tire to which the present invention is applied has a high effect of preventing the occurrence of groove cracks and a high effect of preventing cut growth.

Although the tire 10 of this embodiment has a radial structure, the present invention can also be applied to a pneumatic tire having a bias structure.

[0042]

As described above, in the aircraft pneumatic tire according to the present invention, the driving density of the non-stretchable cord of the protective layer is reduced in the area corresponding to the circumferential groove with respect to the area corresponding to the land. By setting the density, cracks in the rubber layer between the cords in the area corresponding to the circumferential groove can be prevented, and an excellent effect of reliably preventing the occurrence of groove cracks can be obtained.

[Brief description of the drawings]

FIG. 1 is an enlarged cross-sectional view of a tread portion of a tire according to the present invention and its periphery.

FIG. 2 is a meridional sectional view of a tire according to the present invention (however, hatching of a rubber layer is omitted).

FIG. 3 is a plan view of a protective layer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Tire 12 Carcass 22 Tread part 28 Groove 29 Land part 30 Protective layer (reinforcing layer) 32 Aramid cord

Claims (1)

(57) [Claims] 1. A toroidal carcass, a tread portion provided on a crown portion of the toroidal carcass and in contact with a road surface, and a plurality of circumferential grooves provided on the tread portion and extending along a tire circumferential direction. A plurality of land portions, and reinforcement formed by arranging a plurality of non-stretchable cords buried in the base of the tread portion and extending substantially in a sine curve along the tire circumferential direction in the tire axial direction. A pneumatic tire for an aircraft, wherein a driving density of the non-shrinkable cord is lower in a region corresponding to the circumferential groove than in a region corresponding to the land portion.