JPH0648106A - Bias tire for heavy load - Google Patents

Abstract

PURPOSE:To improve the durability for the cord cut due to the compression fatigue of a carcass at a bead part. CONSTITUTION:The bead part 10A of a bias tire 10 for heavy load is equipped with two bundles of bead cores 12 and 14 which are arranged in the tire axial direction. Between two bundles of bead cores 12 and 14, an outside carcass layer 24 and an inside carcass layer 26 each of which consists of four plies which are inclined with respect to a tire equator plane 22 are succesively turned up. Further, on the outside of the outside carcass layer 24, an outermost carcass layer 27 consisting of two pieces of down carcass is installed, and a bead reinforcing band 38 is arranged in the height region in 2/3 of the tire max. width height T from the lower part of a rim separation point P. The bead reinforcing band 38 is formed by spiral-winding at least one organic fiber cord covered with rubber in the tire circumferential direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heavy load bias tire, and more particularly to a heavy load bias tire having improved bead durability.

[0002]

2. Description of the Related Art Conventionally, in a heavy-duty pneumatic bias tire used for trucks, buses and the like, the carcass has a multi-layer structure because the internal pressure becomes extremely high. Therefore,
In order to secure the strength of a pair of beads supporting both ends of these carcass and improve the bead durability, it is known that a plurality of bead cores arranged in the tire axial direction are provided in the bead portion. It is also known that a bead reinforcing layer is provided on the outer side of the carcass layer in the tire axial direction.

For example, in the tire disclosed in JP-A-60-183208, as shown in FIG.
No. 0 bead portion 70A is provided with two bundles of bead cores 72, 74 arranged in the tire axial direction (the left-right direction in FIG. 4). At least eight carcasses having a bias structure (not shown) are stretched around these bead cores 72 and 74. Further, on the outer side of the outermost carcass 76 in the tire axial direction in the bead portion 70A, a canvas chafer 78 made of a cord cloth in which organic fiber cords are embedded in rubber, and an edge portion of the outermost carcass 76 to the canvas chafer 78 are formed. Rubber chafer 8 separating 78A
0 is placed.

However, in the tire 70, the canvas chafer 78 and the rubber chafer 80, which are bead reinforcing bands, have only the function of protecting and reinforcing the friction between the bead portion 70A and the rim portion 82.

On the other hand, in terms of durability of the bead portion of a heavy load bias tire, in addition to rubbing between the tire and the rim, it is more important that the cord breaks due to the compression fatigue of the carcass due to repeated deformation during load rolling. Endurance against.

[0006]

SUMMARY OF THE INVENTION In consideration of the above facts, an object of the present invention is to obtain a heavy-duty bias tire capable of improving durability against cord breakage caused by compression fatigue of a carcass at a bead portion. is there.

[0007]

A heavy-duty bias tire according to the present invention according to claim 1 has a plurality of bead cores, and a carcass layer made of an organic fiber straddling between the bead cores in a toroidal shape, and the carcass layer. In a heavy-duty bias tire having a breaker and a tread on the outer peripheral side of the tire, a tire shaft of the outermost carcass is provided in a region between a rim separation point of a bead portion and a height of ⅔ of a maximum tire width. A bead reinforcing band formed by spirally winding one or more organic fiber cords covered with rubber in the tire circumferential direction is provided on the outer side in the direction.

[0008]

The nylon cord generally used for the carcass of the heavy duty bias tire is repeatedly subjected to compressive strain and fatigues, leading to cord breakage. Also, the tire bead part is
When the tire is loaded, it receives bending deformation and shear deformation in the tire circumferential direction, and the ply cord of the outermost carcass receives the maximum compression strain, causing cord breakage. In order to reduce the compression strain of the cord of the outermost carcass, it is important to suppress the shear deformation in the tire circumferential direction.

Therefore, in the heavy load bias tire according to the first aspect of the present invention, the tire of the outermost carcass is located in a region between the rim separation point of the bead portion and the height of 2/3 of the maximum tire width. By arranging a bead reinforcement band in which one or more organic fiber cords spirally wound in the circumferential direction are covered with rubber on the outer side in the axial direction, shear deformation in the tire circumferential direction of the bead portion is most effectively suppressed, Improves durability against cord breakage due to carcass compression fatigue at the bead.

The bead reinforcement band is arranged at the rim separation point at the radially outer end (here, the rim separation point is 70% of the height H of the flange 34 of the rim 32, as shown in FIG.
It is the intersection point P with the outer peripheral surface of the tire with the flange inner wall 34A at the position. Above, the effect of suppressing the shear deformation of the bead portion is reduced. When the radially inner end is ⅔ or more of the tire maximum width height, the effect of suppressing the shear deformation of the bead portion is substantially constant. For this reason, it is preferable that the bead reinforcing band is arranged in a region between the lower side of the rim separation point and the height of 2/3 of the maximum tire width.

[0011]

EXAMPLE An example of a heavy duty bias tire of the present invention will be described with reference to FIGS.

As shown in FIG. 1, the heavy load bias tire 10 of this embodiment has a size of 23.5-25, and the bead portion 10A of the heavy load bias tire 10 is large.
Is provided with two bundles of bead cores 12 and 14 arranged in the tire axial direction (the left-right direction in FIG. 1). Further, on the tire radial direction outer side of the two bundles of bead cores 12 and 14 (upper side in FIG. 1), a triangle-shaped outer bead portion and a tire axial direction inner bead portion are formed by the bead cores 12 and 14 The bead epex rubbers 18 and 20 are arranged.

An outer carcass layer 24 and an inner carcass layer 26 each consisting of four plies inclined with respect to the tire equatorial plane 22 are straddled between the two bundles of bead cores 12, 14 and wound up one after another. ing. Further, an outermost carcass layer 27 composed of two down carcasses is provided outside the outer carcass layer 24, and the end portions of the two down carcass serve as toe stoppers for the bead portion 10A.

In the bead portion 10A, on the outer side of the outermost carcass layer 27 in the tire axial direction, the rim separation point P, that is, the rim 3 is formed.
2 from the lower side of the intersection P with the tire outer peripheral surface with the flange inner wall 34A at a position 70% of the height H of the flange 34, to the region between the height of 2/3 of the tire maximum width height T and the bead. A reinforcing band 38 is arranged.

As shown in FIG. 2, the bead reinforcing band 38 is formed by spirally winding one or more (one in this embodiment) organic fiber cords 42 covered with rubber 40 in the tire circumferential direction. The organic fiber cord 42 is made of, for example, nylon 1890d / 2, d = 2.5 mm.

As shown in FIG. 1, the outermost carcass layer 2
A breaker 29 and a tread 2 are provided on the outer side in the tire radial direction of 7.
8 are provided. In this tread 28, one end 30A is opened at the tread end, and the other end 30B is closed in the tread central region, and lug grooves 30 are alternately arranged in the tire circumferential direction on the left and right sides of the tire equatorial plane 22. It is arranged.

Next, the operation of this embodiment will be described. In the heavy duty bias tire 10 of this embodiment, the bead portion 10A is used.
One or more organic fibers spirally wound in the circumferential direction on the outer side of the outermost carcass 27 in the axial direction of the tire in a region between the lower rim separation point P and a height of 2/3 of the tire maximum width height H. Bead reinforcement band 38 in which cord 42 is covered with rubber 40
Was placed. Thereby, the shear deformation of the bead portion 10A can be effectively suppressed, and the durability against the cord breakage due to the compression fatigue of the carcass at the bead portion 10A is improved.

With respect to the arrangement position of the bead reinforcing band 38, when the radially outer end 38A is above the rim separation point P, the effect of suppressing the shear deformation of the bead portion 10A is reduced. Further, the radially inner end 38B is ⅔ of the tire maximum width height T.
With the above, the effect of suppressing the shear deformation of the bead portion 10A is substantially constant. For this reason, the bead reinforcing band 38 is disposed at a position from below the rim separation point P to the tire maximum width height T of 2
The area between the heights of / 3 is preferred.

In the heavy load bias tire 10 of this embodiment, as shown in FIG. 2, the bead reinforcing band 38 is used.
1 has a structure in which one organic fiber cord 42 is covered with the rubber 40. Instead of this, as shown in FIG. 3, the bead reinforcing band 38 is used, and the two organic fiber cords 42 are used in the rubber 4
A structure covered with 0 may be used. Further, a structure in which three or more organic fiber cords are covered with rubber may be used.

(Test Example) The heavy duty bias tire of the present example shown in FIG. 1, the tire of the comparative example and the tire of the conventional example shown in FIG. The bead durability was tested by the following evaluation method. That is, each tire was mounted on a drum tester with an outer diameter of 5 m, and the internal pressure was 3 kgf / cm ² and the load was 7100 kg of 140.
%, Drive straight ahead at a speed of 5 km / h, measure the time until the cord breaks at the bead, and the result is 10
The bead durability index, which was set to 0, is shown in Table 1. The larger the index, the better.

[0021]

[Table 1]

From the results shown in Table 1, it is clear that the heavy load bias tire of the present invention is excellent.

[0023]

Since the heavy duty bias tire of the present invention has the above structure, it has an excellent effect that the durability against the cord breakage due to the compression fatigue of the carcass at the bead portion can be improved.

[Brief description of drawings]

FIG. 1 is an axial sectional view showing a part of a heavy duty bias tire according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a bead reinforcing band of a heavy duty bias tire according to an embodiment of the present invention.

FIG. 3 is a cross-sectional view showing a bead reinforcing band of a heavy duty bias tire according to another embodiment of the present invention.

FIG. 4 is an axial cross-sectional view showing a bead portion of a conventional bias tire.

[Explanation of symbols]

 10 Heavy load bias tire 10A bead portion 12 Tire axial outer bead core 14 Tire axial inner bead core 24 Outer carcass layer 26 Inner carcass layer 27 Outermost carcass layer 28 Tread 29 Breaker 32 Rim 34 Flange 38 Bead reinforcement band 40 Rubber 42 Organic fiber cord P Rim separation point T Maximum tire width

Claims (1)

[Claims] 1. A carcass layer comprising a plurality of bead cores and made of an organic fiber straddling the bead cores in a toroidal shape,
In a heavy-duty bias tire having a breaker and a tread on the tire outer peripheral side of the carcass layer, a tire maximum width height of 2 /
In the region between the heights of 3, the outermost carcass has a bead reinforcing band formed by spirally winding at least one organic fiber cord covered with rubber in the tire circumferential direction on the outer side in the tire axial direction. A characteristic heavy duty bias tire.