JPH01114502A - Pneumatic radial tyre for aircraft - Google Patents

Abstract

PURPOSE:To improve the durability and the partial wear resistance of the tyre in the title by constituting the tire with a toroid shape carcass, a crossing belt layer and a belt layer in the circumferential direction composed of an organic fiber cord with a specified cord angle respectively and specifying the constitution of abovementioned respective layers thereof. CONSTITUTION:By an organic fiber cord arranged in parallel, a toroid shape carcass 1 with a cord angle 70-90 deg., a crossing belt layer 2 with a cord angle 10-70 deg. and a belt layer 3 in the circumferential direction in parallel with the circumferential direction are formed respectively. The crossing belt layer 2 is composed of plural layers so that the number of layer in the tread side area in made layer than that of a central area. Contrarily, the tread layer 3 in the circumferential direction is built up in such a way like the number of layer in the central area is more than that in the side area. The lowest layer out the belt layers 3 in the circumferential direction is composed of a continuous layer spread over the both side area. Further, a difference in the number of the layer between the central area and the side area is set up like it is layer for crossing belt layer 2 than the belt layer 3 in the circumferential direction. By this composition, the durability and partial wear resistance can be improved simultaneously.

Description

Detailed Description of the Invention (Field of Industrial Application) This invention relates to a pneumatic radial tire for aircraft that is used under high loads and high speeds, and in particular improves durability and uneven wear resistance by improving the belt structure. At the same time, we will discuss the techniques that can be improved.

(Prior art) Radial or semi-radial tires for aircraft are used particularly at high speeds, so in order to resist standing waves, the cords are arranged substantially parallel to the tire's equator (hereinafter referred to as the circumferential direction). This structure is advantageous in terms of weight reduction because it can satisfy the pressure resistance test required for aircraft tires (not breaking at an internal pressure four times the operating internal pressure) with a minimum number of belts. , which is significant in terms of weight or low heat generation, which affects aircraft operating costs. On the other hand, with this structure, the belt cords are arranged in the circumferential direction, making it difficult for the belt to expand and contract during transfers, and because the diameter of a portion of the shoulder is smaller than the center of the tread, a portion of the tread shoulder is dragged during transfers, causing uneven wear. ,
The problem was solved with the following belt structure.

That is, as described in Japanese Patent Application Laid-Open No. 61-196804, it is a structure in which a cross belt layer intersecting the equator of the tire and a circumferential belt layer are used together.

(Problems to be Solved by the Invention) In the case of this belt structure, uneven wear can be reduced by increasing the number of intersecting belt layers, which are easier to expand and contract than the circumferential belt layers.
Since the cross belt layer has lower circumferential rigidity than the circumferential belt layer, the number of belts is inevitably required to satisfy the pressure test, which is disadvantageous in terms of weight, and the thickness of the belt part increases. There was a problem in that the amount of heat generated increased and the durability against separation of the belt portion also decreased.

Therefore, an object of the present invention is to provide a belt structure that can advantageously solve the above problems and simultaneously improve uneven wear resistance and durability.

(Means for Solving the Problem) The inventors aimed to prevent uneven wear by using a combined structure of a circumferential belt layer and a cross belt layer, and to reduce durability caused by an increase in heat generation due to an increase in the number of belts. In order to solve this problem, we conducted a detailed study of the deformation behavior of the belt during pressure tests and rolling, and found that changing the belt structure between the center and side areas of the tread improves uneven wear resistance and It has been found that this method is effective in achieving both durability.

That is, this invention consists of a plurality of plies in which organic fiber cords are arranged parallel to each other at a cord angle of 70 to 90 degrees with respect to the equatorial plane of the tire, and at least one ply is arranged inward of the tire around a pair of bead cores. A toroidal carcass having a folded part, which is wound outward from the tire, and consists of at least two cord layers in which organic fiber cords are arranged parallel to each other and arranged at a cord angle of 10 to 70 degrees with respect to the equator of the tire. , a circumferential belt consisting of a crossed belt layer in which cord layers are laminated in such a manner that the cords intersect with each other, and at least two cord layers in which organic fiber cords are arranged in parallel to each other and are arranged substantially parallel to the equator of the tire. The cross belt layer has a number of layers in the tread side area of the tire that is greater than the number of layers in the tread center area, and the circumferential belt layer has a number of layers in the tread center area than the number of layers in the tread side area. At least one of the many circumferential belt layers is a continuous layer extending between both side areas of the tread, and the difference in the number of layers between the tread side area and the tread center area in the cross belt layer and the circumferential belt layer is determined by the cross belt layer. This pneumatic radial tire for aircraft is characterized by having a smaller circumferential belt layer.

In the pneumatic radial tire for aircraft according to the present invention, the intersecting belt layers disposed in the tread side regions and the circumferential belt layers disposed in the tread central region are located at substantially the same distance from the rotation axis of the tire. Substantially constitutes one layer, and furthermore, the discontinuous point between the cross belt layer and the circumferential belt layer ranges from 35 to 75% of the length from the center of the tread contact width as the starting point to the tread contact edge. at least one of the intersecting belt layers is a continuous layer spanning the tread side loading; the circumferential belt layer and the intersecting belt layer are made of organic fiber cords made of the same material; at least one of the intersecting belt layers The layer is comprised of a folded ply; At least one layer of the circumferential belt layer is a dividing layer divided into one side region of the tread and the other; More preferably, the dividing layer is the outermost layer of the circumferential belt layer. And, it is recommended as an embodiment that the end of the split layer on the tread center area side is located in a range of 35 to 75% of the length from the center of the tread contact width as a starting point to the tread contact edge. .

Now, FIG. 1 illustrates the structure of an aircraft tire according to the present invention.

In the figure, 1 is a carcass, 2 is a cross belt layer, 3 is a circumferential belt layer, 4 is a tread, and 5 is a bead core.

In this example, the carcass 1 is made up of four turn-up plies wound around the bead core 5 from the inside of the tire to the outside, and one down ply extending toward the bead toe along the outside of the turned-up ply. It becomes an up-down stack.

The cross belt layer 2 consists of folding both sides of a ply made of organic fiber cords, placing one layer in the tread side area by the folded ply, and placing one layer covering the tread side loading between two cord layers made of one ply. One additional ply is added only to the ply and the tread side area, and the tread center area has two cord layers and the tread side area has four cord layers, and the difference in the number of layers between the two is two layers. In the illustrated example, the ply end wraps around the inner cross heald end to prevent shear strain from occurring at the folded ply end.

The circumferential belt layer has four consecutive cord layers with a load on both tread sides, which are constructed by spirally wrapping organic fiber cords made of the same material as the cross belt layer in the circumferential direction of the tire. Two cord layers are placed in the center area of the tread between the belt layers, and one cord layer is placed only in the side area of the tread.
By adding plies one by one, there are 6 cord layers in the center area of the tread and 5 layers in the side areas of the tread, and the difference in the number of layers between the two is 1 layer.

Therefore, there are two belt layers in which the cross belt layer is arranged in the tread side region and the circumferential belt layer is arranged in the tread center region. Note that the discontinuity point P between the cross belt layer and the circumferential belt layer in these layers is the length of the tread contact width from the center to the tread contact end (
L/2).

FIGS. 2A to 2E also show radial cross sections of other belt structures according to the present invention. The solid line indicates the cross belt layer 2, and the dotted line indicates the circumferential belt layer 3.

(Function) In this invention, organic fibers are used for the cords constituting each belt layer. The organic fiber cords shrink due to heat, and generate heat shrinkage stress due to the effect of vulcanization heat. This is because the initial tension of the belt in the circumferential direction increases at times, which effectively acts to suppress standing waves.

On the other hand, a certain number of belts is required to satisfy the pressure resistance of aircraft tires, but the growth of the outer diameter of the tire due to air flow, especially the growth of the belt, is limited by the sidewalls, which have little effect on suppressing growth. As shown in Fig. 3, the center part is large, and the elongation in this part affects the belt breakage in the pressure test.

However, during load transfer, the deformation of the belt in the center of the tread is small, and the closer it gets to the contact edge of the shoulder part, which has a large difference in outer diameter from the center of the tread, the greater the deformation. To prevent this, it is sufficient to ensure belt elasticity in the shoulder area, and since belt deformation is small in the central tread area under load, even if a circumferential belt layer is placed, it will not have a negative effect on uneven wear. do not have.

From the above, in a belt structure consisting of a circumferential belt layer and a crossed belt layer, the number of circumferential belt layers in the tread center region of the belt layer is greater than the number of circumferential belt layers in the tread side region including the ground contact edge, On the other hand, by arranging the number of intersecting belt layers in the tread side region greater than the number of intersecting belt layers in the central part, it is possible to provide a tire that satisfies the specified pressure resistance test without significantly increasing the number of belts. Furthermore, heat generation in the belt portion can be suppressed, resulting in excellent durability and uneven abrasion resistance.

However, if the circumferential belt layer is placed only in the center area of the tread, part of the shoulder will grow due to centrifugal force during high-speed rotation, easily generating standing waves and causing separation at the edge of the belt. At least one of the belt layers must be disposed over the tread side loading.

In addition, since the cross belt layer has lower circumferential rigidity than the circumferential belt layer, the difference in the number of layers between the central region and the side region of the tread (hereinafter simply referred to as the difference in the number of layers) is the difference between the cross belt layer and the circumferential belt layer. If they are equal, the circumferential stiffness in the tread side regions where the ratio of intersecting belt layers to all belt layers is high is lower than that in the tread center region, resulting in a belt structure in which the circumferential stiffness is non-uniform in the tire axial direction.

With this belt structure, the radius of curvature of the crown becomes large in a part of the shoulder because the shoulder part tends to stretch when the internal pressure is applied. Ground contact pressure increases, heat generation in the tread increases, and separation between the tread and the belt is likely to occur.

Therefore, it is important to make the difference in the number of layers smaller in the circumferential belt layers than in the intersecting belt layers, and to make the circumferential rigidity uniform between the tread center region and side regions.

In addition, even in the above belt structure, when a load is applied, the belt part undergoes bending deformation in the thickness direction, and the area near the carcass layer experiences greater deformation than the other areas. Therefore, when the load is transferred, the carcass layer in the tread side area, where belt elongation is large in the circumferential direction, undergoes bending deformation. The belt structure according to the invention, which has multiple intersecting belt layers in close regions, hardly impairs the uneven wear resistance.

In this invention, it is more advantageous to satisfy the following conditions under the above-mentioned basic configuration. That is, in order to suppress the increase in the thickness of all belt layers in the tread center region and improve durability, the cross belt layers arranged in the tread side regions and the circumferential belt layers arranged in the tread center region are substantially 1N. Here, it is preferable that the discontinuity point between the cross belt layer and the circumferential belt layer be located in a range of 35 to 75% of the length from the center of the tread contact width to the contact edge for the following reason.

Figure 3 shows the circumferential elongation distribution of the belt during pressure resistance tests and load transfer using an index with the maximum value as 100.
During the pressure resistance test, belt elongation was large in the region of less than 35% of the tread contact width, while during load transfer, on the other hand, deformation at the center of the contact width was small, and belt elongation occurred in some shoulder regions exceeding 75% of the contact width. is big. °Therefore, by setting the position of the discontinuity between the cross belt layer and the circumferential belt layer within the above-mentioned range, the circumferential belt layer in the center area of the tread can effectively contribute to ensuring rigidity in the pressure test, while at the same time At the time of transfer, a cross belt layer that is easy to stretch is arranged in a part of the shoulder where deformation is large, and the circumferential belt layer restrains deformation in this area, so that uneven wear resistance is not adversely affected.

If the crossed belt layers are placed only in the tread side areas, the central tread area will have only the circumferential belt layer, and since no belt cords are placed in the tread width direction, the rigidity in the tire rotational axis direction and shear rigidity will be extremely low. A large rigidity difference occurs between the tread side area where the crossed belt layer is placed,
Stress concentration occurs at the boundary, which tends to cause failures such as separation. Therefore, it is desirable that at least one of the cross belt layers be a continuous layer over the tread side load.

From the viewpoint of alleviating stress concentration between the eyebrows at the edge of the crossed belt layer, it is preferable that at least one layer of the crossed belt layer is made of a folded ply.

A belt structure that easily expands and contracts in the circumferential direction of the tire during load transfer alleviates the shearing deformation of the tread caused by the difference in the outer circumference between the center part of the tread on the tire tread and part of the shoulder, thereby reducing uneven wear caused by dragging part of the shoulder. can be suppressed. During load transfer, the belt part undergoes bending deformation directly under the load, and the region away from the tread, that is, the region adjacent to the carcass layer, is stretched more circumferentially. Therefore, a cross belt layer that is more elastic in the circumferential direction is provided in that region. It is effective to place

In addition, in the basic configuration described above, there may be a structure in which there is no circumferential belt layer between the divided intersecting belt layers (hereinafter referred to as the middle part), but in this case, even if the space in the middle part is filled with a rubber sheet, the vulcanization At times, manufacturing defects such as belt disorder in which the ply of the upper circumferential belt layer falls into the middle part due to rubber flow or contraction of the belt cord are likely to occur. Therefore, it is preferable to arrange a split layer in which plies are arranged only in the tread side region on the outermost side where there is no risk of ply falling from above. Furthermore, the end of the split layer on the tread center area side is
As with the continuous point P in the cross belt layer, it is more preferable that the continuous point P is located in a range of 35 to 75% of the length from the center of the tread contact width as a starting point to the tread contact end.

(Example) Figure 1 shows the structure of a carcass used for an aircraft tire with a tire size of 46x1B and 0R20. It is arranged.

Tires with belt layers shown in FIGS. 4(A) to (D), in which the intersecting belt layers are shown by solid lines and the circumferential belt layers are shown by broken lines, were manufactured, and for each tire, the weight of the belt part, the pressure resistance test burst pressure, The belt durability and uneven abrasion (amount of wear on part of the shoulder lip) were investigated, and the results are listed in the table below along with the specifications of each belt layer.

In addition, in the examples, the discontinuity point between the circumferential belt layer and the cross belt layer and the end of the dividing layer in the circumferential belt layer on the tread center region side are from the center of the tread contact width as the starting point to the tread side end. It was set at 50% of the length up to.

In the above table, pressure test and belt durability test are FAA
Based on 91 rating, regarding belt durability, Q m1
After increasing the speed from 225 m1le/h to 225 m1le/h, the takeoff simulation was repeated up to 50 times to remove the load, and if the test was completed, the tires were dissected and the state of cracks in the belt was compared.

Regarding uneven wear, some lips of the tread sill were worn out after an accelerated wear test on a drum! (Average wear depth of each rib) is expressed as an index when the wear amount of the rib at the center is set as 100. The closer the value is to 100, the more wear the shoulder rib wears to the rib at the center of the tread. Close (indicates that the uneven wear on the shoulders of some seals has been improved).

Regarding durability under overload (some tires are banked, etc.), it indicates the degree of increase in heat generation due to increase in ground pressure at the tread side area.At overload of 150% of normal load. 111B increases the speed from Om1le8 to 225 m1le8! The maximum temperature at the side area of the tread during shear emission was measured, and the results are expressed as an index with the example as 100.

As is clear from the table, the tire of the present invention satisfies the pressure resistance without significantly increasing the belt weight and without deteriorating the belt durability, and is also safe because the belt temperature does not increase excessively even in the event of an overload. It can be seen that the properties are further improved, and at the same time, the uneven wear resistance is also significantly improved.

(Effects of the Invention) The aircraft tire of the present invention can improve durability and uneven wear resistance, and can simultaneously achieve improvements in each characteristic at a high level, which has been difficult in the past.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of an aircraft tire according to the present invention, Figs. 2 (A) to (E) are explanatory diagrams showing the structure of other belt layers, and Fig. 3 shows circumferential elongation of the belt in each region of the tread. The graphs and FIGS. 4(A) to 4(0) are explanatory diagrams showing the structure of the belt layer. l...Carcass 2...Cross belt layer 3...
- Circumferential direction bell l-N 4... Tread 5... Bead core patent applicant Bridgestone Corporation Figure 2 (A CCC) (B) (i). (Fig. 3

Claims (1)

[Scope of Claims] 1. Consisting of a plurality of plies of organic fiber cords arranged in parallel to each other at a cord angle of 70 to 90 degrees with respect to the equatorial plane of the tire, at least one ply is arranged around a pair of bead cores. a toroidal carcass having a folded part, which is wound from the inside to the outside of the tire;
a cross belt layer consisting of a layer of cords, the cord layers being laminated in such a way that the cords intersect with each other; and at least two cord layers comprising organic fiber cords arranged in parallel to each other substantially parallel to the equator of the tire. The cross belt layer has a circumferential belt layer in which the number of layers in the tread side area of the tire is greater than the number of layers in the tread center area, and the circumferential belt layer has a number of layers in the tread center area of the tire that is greater than the number of layers in the tread center area. at least one layer of the circumferential belt layer is a continuous layer extending between both side regions of the tread, and the difference in the number of layers between the tread side region and the tread center region in the cross belt layer and the circumferential belt layer. is a pneumatic radial tire for aircraft, characterized in that the circumferential belt layer is smaller than the cross belt layer.