JPH04183615A - Pneumatic radial tire for heavy load use - Google Patents

Abstract

PURPOSE:To prevent the variation in the amount of sulfur, and to enhance the separation resistance of a carcass layer by providing a sulfur-included rubber layer between the carcass layer and an innermost bead-part reinforcing layer, and also by specifying the distance between the cord of the carcass layer and that of the innermost bead-part reinforcing layer. CONSTITUTION:Around a bead core 1, a carcass layer 2 consisting of steel cords is folded back and wound up from the inside of a tire and to the outside thereof. In this case, on the outer circumference of the folded-back part of the carcass layer 2, two sheets of bead-part reinforcing layers 3a, 3b consisting of organic fiber cords are provided via a rubber layer 4 so as to extend from the inside of the tire to the outside. And the rubber layer 4 is made up of a rubber compound having the similar composition as the coat rubber forming the carcass layer 2, and also is included therein nearly the same ratio of sulfur as the sulfur content of the coat rubber in the carcass layer 2. And the distance D between the steel cord 20 of the carcass layer 2 and the organic fiber cord 30 of the innermost bead-part reinforcing layer 3a is set to be at least two times the diameter d of the organic fiber cord 30.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a heavy-duty pneumatic radial tire with improved separation resistance of a carcass layer at a bead portion.

[Conventional technology]

Conventionally, heavy-duty pneumatic radial tires (hereinafter referred to as heavy-duty tires) have been manufactured by wrapping a carcass layer 2 made of steel cord around a bead core 1 by folding it back from the inside to the outside of the tire, as shown in FIG. Bead reinforcement layers 3a and 3b made of two organic fiber cords are arranged on the outside of the surrounding carcass layer, and these two
The durability of the bead portion is improved by arranging a bead portion reinforcing layer 3c made of one sheet of organic fiber cord so as to cover the end bundle portion of the carcass layer winding side of the bead portion reinforcing layer.

Incidentally, when reassembling the rim of a heavy-duty tire, a device such as a lever is pushed between the rim and the bead portion, and thus the bead portion may be damaged. When the bead portion is damaged in this way, there is a problem in that water enters the carcass layer from the damaged portion through the bead portion reinforcing layer, which deteriorates the separation resistance of the carcass layer.

According to the inventors' investigation into the cause of this, the amount of sulfur contained in the carcass layer coating rubber and the bead reinforcement layer coating rubber is greater than that of the carcass layer in order to increase the rigidity of these layers. It turns out that this is related to the fact that the reinforcement layer is smaller. In other words, sulfur contained in the carcass layer migrates to the bead reinforcing layer through the water that has entered the carcass layer from the damaged area of the bead part through the bead reinforcing layer, causing a change in the amount of sulfur in the coated rubber of the carcass layer. This is because the adhesion between the coated rubber of the carcass layer and the steel cord is deteriorated. If the adhesion deteriorates, the coated rubber of the steel cord will separate, that is, separation will occur.

[Problem to be solved by the invention]

The present invention was conceived in view of the above-mentioned circumstances, and the present invention suppresses the migration of sulfur between the bead reinforcing layer and the carcass layer, which is caused by water that has entered from the damaged part of the bead. An object of the present invention is to provide a heavy-duty pneumatic radial tire that suppresses fluctuations in the amount of sulfur in the carcass layer and improves separation resistance between the coated rubber of the carcass layer and the steel cord.

[Means to solve the problem]

The present invention provides a heavy-load vehicle in which the ends of a carcass layer made of steel cord are folded back and rolled up around a bead core, and at least one bead reinforcing layer made of organic fiber cord is provided on the outside of the rolled-up portion of the carcass layer. In the pneumatic radial tire, a rubber layer containing sulfur in a proportion approximately equal to the sulfur content of the coat rubber of the carcass layer is provided between the carcass layer and the innermost bead reinforcing layer that are adjacent to each other, and the carcass layer further comprises: The distance between the cords and the innermost bead reinforcing layer is at least twice the diameter d of the organic fiber cord of the innermost bead reinforcing layer.

In this way, in the present invention, a rubber layer is provided between the mutually adjacent carcass layer and the innermost bead reinforcing layer, and the sulfur content of this rubber layer and the sulfur content of the carcass layer are balanced in a certain relationship, Furthermore, because the distance between the cords between the carcass layer and the innermost bead reinforcing layer is set to be more than twice the diameter of the organic fiber cord in the innermost bead reinforcing layer, water that has entered from the damaged part of the bead can be used as a medium. It is possible to prevent sulfur from migrating between the bead reinforcement layer and the carcass layer. Therefore, it is possible to ensure good adhesion of the coated rubber to the steel cord of the carcass layer and improve separation resistance.

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 shows one of the bead structure of the heavy-duty tire of the present invention.
It is a cross-sectional explanatory view showing an example. In this figure, the bead core 1 is surrounded by a carcass layer 2 made of steel cord.
is folded and rolled up from the inside of the tire to the outside, and two bead reinforcing layers 3 made of organic fiber cords are attached to the outer periphery of the folded part of the carcass layer 2 with a rubber layer 4 interposed therebetween.
a and 3b are provided extending from the inside of the tire to the outside. Furthermore, the bead portion reinforcing layer 3a.

Bead reinforcement layer 3 made of organic fiber cord on the outside of 3b
c is placed.

In FIG. 1, there is one carcass layer and three bead reinforcement layers, but the carcass layer may have multiple layers, and the bead reinforcement layer may have one or more layers.

The rubber layer 4 interposed between the carcass layer 2 and the innermost bead reinforcing layer 3a is made of a rubber compound having the same composition as the coat rubber constituting the carcass layer 2. This rubber layer 4 contains sulfur in a proportion approximately equal to the sulfur content of the coat rubber of the carcass layer 2. In addition, when the sulfur content with respect to 100 parts by weight of rubber constituting the rubber layer 4 is defined as X parts by weight, and the sulfur content with respect to 100 parts by weight of rubber in the coat rubber in the carcass layer 2 is 7 parts by weight, 0.5Y≦
It is preferable that X≦1.5Y, more preferably 0.8Y
It is preferable that ≦×≦1.2Y.

By making the sulfur content of the rubber layer 4 interposed between the carcass N2 and the innermost bead portion reinforcing layer 3a close to the sulfur content of the carcass layer 2 in this way, water intrusion into the bead portion is prevented. Even in this case, fluctuations in the sulfur content in the coated rubber of the carcass layer 2 can be prevented. Therefore, since the coated rubber of carcass layer 2 maintains good adhesion to the steel cord of carcass layer 2, carcass layer 2
Separation resistance does not deteriorate.

Furthermore, in order to improve the anti-separation effect of the carcass layer 2 based on the rubber layer 4, it is not sufficient to simply specify the sulfur content in the rubber layer 4. For this purpose, as shown in FIG. 2, the distance between the steel cords 20 of the carcass layer 2 and the organic fiber cords 30 of the innermost bead reinforcement layer 3a, which are adjacent to each other with the rubber layer 4 in between, must be , it is necessary to make it at least twice the diameter d of the organic fiber cord 30. This distance is 2 of the diameter d of the organic fiber cord.
If it is less than twice that, the rubber layer 4 becomes too thin and it becomes impossible to suppress the migration of sulfur between the bead portion reinforcing layer and the carcass layer. The thickness D of the rubber layer 4 is not particularly limited, but is preferably 0.3 to 0.8 cm.
It is better to

Furthermore, since this rubber layer 4 is for preventing sulfur migration between the innermost bead reinforcing layer 3a and the carcass layer 2, as shown in FIG. Rubber layer 4 on the side (outside of the tire)
The height A from the position corresponding to the outer diameter of the terminal rim is P≦
AIR, and consideration should be given so that the height B from the position corresponding to the outer diameter of the rim at the end of the rubber layer 4 on the winding side (inside the tire) of the bead reinforcing layer satisfies Q≦B<R.

Here, P is the height Q from the position corresponding to the outer diameter of the rim to the rolled-up end of the carcass layer 20 when the tire is mounted on a regular rim and in an unloaded state with air filled to the regular internal pressure. The height R from the position corresponding to the outer diameter to the end of the innermost bead reinforcing layer 3a on the inside of the tire is the height from the position corresponding to the outer diameter of the rim to the tire maximum width position.

If this rubber layer 4 exceeds the height R at the tire's maximum width position and extends to the crown, the total gauge of the tire will become thicker, and the tire will be more likely to generate heat due to bending during tire transfer, which will reduce the durability of the tire. I don't like it from above.

In the present invention, the composition of rubber N4 is as follows except that the sulfur content is close to that of the coat rubber of carcass layer 2.
Other compounds can be arbitrarily selected in consideration of adhesion to the carcass layer 2 and the innermost bead reinforcing layer 3a.

Examples are shown below.

〔Example〕

The following two types of tires of the present invention and a conventional tire were manufactured. All these tire sizes are the same 100OR201
It was named 4PR.

The present Kaifuji 2 has a bead structure shown in FIG. 1, and the rubber layer, the coating rubber of each bead reinforcement layer, and the coating rubber of the carcass layer each have a sulfur content of 5.0% per 100 parts by weight of rubber.
5 parts by weight, 4.0! A rubber composition of 6.0 parts by weight was used for the placing part, nylon fiber cord 840 D/2 was used for the organic fiber cord of the innermost bead reinforcement layer, and 3 + 9 + 15 (0,175) was used for the carcass cord. '' steel cord was used, the distance between the cords between the innermost bead reinforcing layer and the carcass layer was 1.3 mm, and the thickness of the rubber layer D' was 0.5 mm.

Conventional Tire: Same as the tire of the present invention, except that it had the bead structure shown in FIG. 4, no rubber layer was provided, and the distance between the cords was 0.8 mm.

These tires were each given a cut in the bead portion through which water could penetrate, and then the separation resistance of the carcass layer was evaluated by the following method.

Separation method: Put 11 water in the tire, 22.5 x 8.25
The bead carcass layer of this tire was mounted on the rim of the tire, and was run for 300 hours at a speed of 45 km/h on a steel drum with a smooth surface of 1707 mm in diameter under conditions of an internal tire pressure of 7.00 kg/cm'' and a load of 4400 kg. A
The coating rubber coating rate of the carcass layer steel cord was measured and evaluated in accordance with STM-D2229.

As a result, the separation resistance of the tire of the present invention was 110
In contrast, the separation resistance of conventional tires is 1
00, indicating that the tire of the present invention had significantly improved separation resistance of the carcass layer.

〔Effect of the invention〕

As explained above, according to the present invention, the end portion of the carcass layer made of steel cord is folded back and rolled up around the bead core, and at least one layer made of organic fiber cord is placed on the outside of the rolled up portion of the carcass layer. In a heavy-duty pneumatic radial tire provided with a bead reinforcing layer, sulfur is contained between the mutually adjacent carcass layer and the innermost bead reinforcing layer in a proportion approximately equal to the sulfur content of the coat rubber of the carcass layer. A rubber layer is provided, and the distance between the cords between the carcass layer and the innermost bead reinforcing layer is determined by the diameter d of the organic fiber cord of the innermost bead reinforcing layer.
Even if water intrudes from the damaged portion of the bead portion that occurs when the rim is reassembled, it is possible to prevent fluctuations in the amount of sulfur in the coated rubber of the carcass layer. Therefore, since good adhesion of the coat rubber of the carcass layer to the carcass cord can be maintained, it is possible to improve the separation resistance of the carcass layer.

[Brief explanation of drawings]

FIG. 1 is an explanatory cross-sectional view showing an example of the bead structure of the pneumatic radial tire for heavy loads according to the present invention, and FIG. 2 is an explanatory cross-sectional view showing the carcass layer and innermost bead reinforcing layer of the same tire. , FIG. 3 is an explanatory half-sectional view in the meridian direction of the tire to explain the arrangement position of the rubber layer in the pneumatic radial tire for heavy loads of the present invention, and FIG. 4 shows an example of the bead structure of a conventional pneumatic radial tire for heavy loads. FIG. 1... Bead core, 2... Carcass layer, 3a, 3
b. 3c... Bead portion reinforcement layer, 4... Rubber layer, D...
Inter-cord distance between the carcass layer and the innermost bead reinforcing layer, d...Diameter of the organic fiber cord of the innermost bead reinforcing layer. Agent Patent Attorney Nobuo Ogawa −

Claims (1)

[Claims] A tire in which the ends of a carcass layer made of steel cord are folded back and rolled up around a bead core, and at least one bead reinforcing layer made of organic fiber cord is provided on the outside of the rolled up part of the carcass layer. A rubber layer containing sulfur in a proportion approximately equal to the sulfur content of the coating rubber of the carcass layer is provided between the carcass layer and the innermost bead reinforcing layer; A pneumatic radial tire for heavy loads in which the distance D between cords is at least twice the diameter d of the organic fiber cord of the innermost bead reinforcing layer.