JPH10129213A - Large-sized pneumatic radial tire for rough road - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a large-sized pneumatic radial tire for a rough road markedly improving belt durability at the time running on the rough road by reforming a belt part. SOLUTION: In a large-sized pneumatic radial tire for a rough road having a pair of bead parts, carcass continued in a toroidal shape to this bead part, and a belt crossing layer fastening a crown part with a hoop of this carcass, a steel chord used in the belt crossing layer is a steel chord of layer twist structure not having a spiral filament, a twist direction of this steel chord is provided with at least one part in a reverse direction between the adjacent belt crossing layers.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a large pneumatic radial tire for rough roads, in which belt durability is greatly improved by improving a belt portion.

[0002]

2. Description of the Related Art In recent years, in order to reduce the cost of steel cords, so-called non-spiral cords, which can eliminate one twisting step and have no spiral filament, have come to be used. In addition, a steel cord having the same direction twist structure, which is considered to have a higher wrapping effect because the cord strength is higher and the bundle is easily deformed as compared with the twist in the different direction, tends to be used.

[0003] When a cut is made in a tire,
In order to prevent water from propagating inside the steel cord of the belt layer and causing the belt end separation to occur and propagate, it is effective to use a so-called rubber pene cord for the belt, in which rubber easily penetrates inside the cord. To do so, the gap between the filaments of the outermost sheath of the cord should be at least 0,0.
It is effective to have a structure of 02 mm, for example, a 3 + 8 structure.

[0004]

However, when a conventional large pneumatic radial tire using a steel cord for a tire belt portion is run on a rough road, a belt end separation (hereinafter referred to as a rough road BES) peculiar to a rough road due to a cut wound. "Abbreviated as"), the tire life is extremely shortened. As a method of improving the wrapping ability of the belt to reduce the possibility of receiving such cuts, it is known to use a so-called hollow belt (see (b) in FIG. 1). B
Actually, many things broken by ES and the like occur.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a large pneumatic radial tire for rough roads in which the belt durability is greatly improved when traveling on rough roads by improving the belt portion.

[0006]

In order to solve the above-mentioned problems, a large pneumatic radial tire for a bad road according to the present invention comprises a pair of beads, a carcass connected to the beads in a toroidal shape, and In a large pneumatic radial tire for bad roads having a belt intersecting layer that holds a crown portion of a carcass, the steel cord used for the belt intersecting layer is a steel cord having a layer twist structure having no spiral filament. The twisting direction of the steel cord is at least one position opposite between adjacent belt interlacing layers.

[0007] The present invention also relates to a large pneumatic radial tire for a rough road, wherein each layer of the steel cord having the layer-twist structure is twisted in the same direction. It is a large pneumatic radial tire.

Further, the present invention provides the large pneumatic rough tire for rough roads, wherein the twisted pitches of the respective layers of the steel cord having the layered structure are different from each other in the large pneumatic radial tire for rough roads. It is a radial tire.

Further, the present invention provides the large pneumatic radial tire for rough roads, wherein the first belt layer of the belt intersecting layer adjacent to the carcass has a hollow structure. Tires.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION A large pneumatic radial tire for rough roads, when stepping on a protrusion, causes the belt cord of the belt intersecting layer to move in the opposite direction for each layer, causing deformation such as lifting of a so-called pantograph. Will act to wrap around, but one factor that determines the ease of wrapping is
This is due to the distortion of the rubber in the belt intersecting layer. That is, when the distortion becomes large and the rubber becomes difficult to expand, it becomes difficult to enclose the rubber.

The present inventor has found that one factor that greatly affects the distortion of the rubber is the twist of the steel cord caused by stepping on the protrusion. In other words, when steel cords having the same twist direction are used for each layer of the belt intersecting layer, the steel cords rotate so as to be unraveled when stepping on the protrusion. As a result, the twist direction of the steel cord in each layer is as shown by the arrow in FIG. 2, and a large shear strain is generated in the rubber between the layers, and the wrapping effect is reduced.

Therefore, the present inventor reversed the twist direction of the cord between the layers based on such knowledge, and found that the twisting direction of the cord became a direction in which the strain applied to the rubber between the layers was reduced, so that the wrapping effect was large. It became clear that it was hard to receive cut damage. It was also found that when the belt-reinforced steel cord had a spiral, the effect of reducing the amount of twist of the cord was reduced by the spiral filament. Furthermore, it has been found that the non-spiral, layer-twisted cord in the same direction has a large amount of twist, particularly in the direction of reducing the strain applied to the rubber between the layers, and therefore, the twist direction of the steel cord is changed in every belt intersecting layer. The large-sized pneumatic radial tire for rough roads arranged in the opposite direction to that described above is much more effective because the rough road BES is significantly reduced as compared with conventional tires.

In the large pneumatic radial tire for rough roads according to the present invention, other conditions such as the driving angle of the belt and the number of belts are not different from the conventionally known conditions of the tire. Further, the twist pitch, twist structure and filament diameter of the steel cord used for the belt are not different from those of the conventional steel cord as long as the conditions of the present invention are satisfied. For example, 3 + 8 for the belt structure
It can be a rubber-penetrated type such as a structure, and the twist angle is 70 ° or more, and the filament diameter is 0.20 to 0.20.
It can be 0.44 mm.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments. Conventional Examples, Examples 1 to 5 and Comparative Examples 1 to 2 Large pneumatic radial tires of size 11R22.5 were prototyped using belt structures and steel cords shown in Table 1 below as belt materials. In addition, the complete type in the belt structure in Table 1 is a normal belt laminated structure shown in FIG. 1A, and the hollow type is a second type adjacent to the carcass layer as shown in FIG. It means a structure in which one belt is so-called hollow.

The control tires of the conventional tires shown in Table 1 have a steel cord of 3 + 9 + 15 ×
It has a structure of 0.23 (mm) +1 and the number of shots is 18.6.
A rubberized cloth is prepared so as to have a size of / 5 cm, and the first belt layer 38 ° and the second to fourth belt layers 72 ° in the tire circumferential direction.
Was used as a belt. A conventional tire having four such belted rubberized fabrics as a belt layer (complete type) was used as a control tire in the following tests. The tires of the examples and comparative examples were the same as the conventional example except for the belt structure. The above-described prototype tires were subjected to the following various tests after ordinary tire molding and vulcanization.

(1) Cut damage: 20 kg / cm ² inner pressure, 100% load, 20% bad road
% After running 100,000 km on the road surface, the tread of the tire was peeled off, and the number of cuts reaching the fourth belt layer was counted.
The number of cuts of the control tire was set to 100 and indicated by an index. The smaller the numerical value, the better the number of cuts.

(2) Connection Ratio (Bad Road BES) The third belt end of the test tire was peeled off, 20 cords were checked, and the ratio of connection between the cords was taken as an index, with the same ratio of the control tire being 100. Displayed. The smaller the value, the better.

(3) Rust Length A third belt treat was cut out from a new tire to be tested, its end was immersed in salt water, and the length of rust development after 24 hours was measured. The measurement method was as follows: the cord was dissected, and the rust length of the core was indicated by the distance from the salt water surface. The results obtained are shown in Table 1 below.

[0019]

[Table 1]

The following is evident from Table 1 above. Conventional belt structure and steel cord used for it
It is a typical one conventionally used. On the other hand, in Example 1, the steel cord used for the second belt layer and the third belt layer was changed as shown in Table 1 above, while the belt structure was kept as it was. As a result, good results were obtained in both the number of cuts, the bad road BES, and the rust length as compared with the conventional example. Further, the second embodiment is an example in which the belt structure of the first embodiment is formed as a hollow structure, whereby the number of cut injuries particularly at the center is reduced as compared with the first embodiment. further,
Example 3 is an example in which the core and the sheath are not twisted in the same direction. In this case, the wrapping effect of the belt is slightly reduced as compared with Example 1, and the number of injuries and the bad road BES are both reduced as compared with Example 1. doing. Furthermore, Example 4 is an example in which the structure of the steel cord is a 3 + 9 structure. In this case, the permeability of the rubber into the cord is reduced, and the rust length is reduced.
It is longer than. The fifth embodiment is an example in which the core and the sheath have the same pitch. In this case, although the rust length was inferior, the number of injuries and the bad BES were good.

On the other hand, Comparative Example 1 is an example in which a steel cord wound with a spiral filament is used for the belt. In this case, the rust caused by the good permeability of rubber into the cord is good. Except that the length was short and good, almost the same results as the conventional example were obtained. Comparative Example 2 is an example in which a steel cord having the same twist structure is used in the second belt layer and the third belt layer. In this case, the number of cut injuries is large, and the bad road BES is also inferior to the conventional example.

[0022]

As described above, in the large pneumatic radial tire for a bad road according to the present invention, the number of cuts and the BES on a bad road are remarkably reduced as compared with the conventional tire of the same kind, and the tire life is shortened. The effect of significantly increasing the length is obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a comparison between a complete belt type and a hollow belt type belt structure.

FIG. 2 is an explanatory view showing a twist direction of a steel cord of each layer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st belt layer 2 2nd belt layer 3 3rd belt layer 4 4th belt layer

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[Procedure amendment]

[Submission date] December 24, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Name of invention

[Correction method] Change

[Correction contents]

[Title of the Invention] Large pneumatic radial tire for rough road

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI D07B 1/06 D07B 1/06 A

Claims (4)

[Claims] A large pneumatic radial tire having a pair of bead portions, a carcass connected to the bead portions in a toroidal shape, and a belt intersecting layer for fastening a crown portion of the carcass; The steel cord used for the belt intersecting layer is a steel cord having a layered structure having no spiral filament, and the twisting direction of the steel cord is at least one location opposite between adjacent belt intersecting layers. Large pneumatic radial tire for rough roads. 2. The large pneumatic radial tire for rough roads according to claim 1, wherein a steel cord having a layer twist structure is used, wherein each layer of the steel cord having the layer twist structure is twisted in the same direction. 3. The large pneumatic radial tire for a bad road according to claim 1, wherein a steel cord having a layer twist structure is used, in which each layer of the steel cord having the layer twist structure has a different twist pitch. 4. The first belt layer of the belt intersecting layer adjacent to the carcass has a hollow structure.
The large pneumatic radial tire for a bad road according to any one of claims 1 to 3.